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Analytical Chemistry

Gary D. Christian, Purnendu K. Dasgupta, Kevin A. Schug

Chapter 5

Stoichiometric Calculations: The Workhorse of the Analyst - all with Video Answers

Educators

Chapter Questions

00:16

Problem 1

Distinguish between the expression of concentration on weight/weight, weight/volume, and volume/volume bases.

David Collins
David Collins
Numerade Educator
00:42

Problem 2

Express ppm and ppb on weight/weight, weight/volume, and volume/volume bases.

Nicole Smina
Nicole Smina
Numerade Educator
01:27

Problem 3

Define the term "equivalent weight," used for electrolytes in clinical chemistry. Why is this used?

Ramesh Singh
Ramesh Singh
Numerade Educator
01:00

Problem 4

List the requirements for a titration. What are the four classes of titrations?

Alkendra Singh
Alkendra Singh
Numerade Educator
00:24

Problem 5

What is the equivalence point of a titration? The end point?

David Collins
David Collins
Numerade Educator
02:15

Problem 6

What is a standard solution? How is it prepared?

Freddie Montague
Freddie Montague
Numerade Educator
00:54

Problem 7

What are the requirements of a primary standard?

Adam Conner
Adam Conner
Numerade Educator
01:03

Problem 8

Why should a primary standard have a high formula weight?

Jorge Villanueva
Jorge Villanueva
Numerade Educator
02:50

Problem 9

Calculate the grams of substance required to prepare the following solutions: (a) $250 \mathrm{~mL}$ of $5.00 \%$ (wt/vol) $\mathrm{NaNO}_{3} ;$ (b) $500 \mathrm{~mL}$ of $1.00 \%$ (wt/vol) $\mathrm{NH}_{4} \mathrm{NO}_{3},$ (c) $1000 \mathrm{~mL}$ of $10.0 \%$ (wt/vol) $\mathrm{AgNO}_{3}$

Thomas Harr
Thomas Harr
Numerade Educator
10:17

Problem 10

What is the wt/vol $\%$ of the solute in each of the following solutions?
(a) $52.3 \mathrm{~g} \mathrm{Na}_{2} \mathrm{SO}_{4} / \mathrm{L},$ (b)
$275 \mathrm{~g} \mathrm{KBr}$ in $500 \mathrm{~mL},$ (c) $3.65 \mathrm{~g} \mathrm{SO}_{2}$ in $200 \mathrm{~mL}$

Marietjie Lutz
Marietjie Lutz
Numerade Educator
11:33

Problem 11

Calculate the formula weights of the following substances:
(a) $\mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O},$ (b) $\mathrm{KHC}_{2} \mathrm{O}_{4}$.
$\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4},$ (c) $\mathrm{Ag}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7},$ (d) $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:42

Problem 12

Calculate the number of millimoles contained in $500 \mathrm{mg}$ of each of the following substances:
(a) $\mathrm{BaCrO}_{4},$ (b) $\mathrm{CHCl}_{3}$,
(c) $\mathrm{KIO}_{3} \cdot \mathrm{HIO}_{3}$
(d) $\mathrm{MgNH}_{4} \mathrm{PO}_{4}$,
(e) $\mathrm{Mg}_{2} \mathrm{P}_{2} \mathrm{O}_{7}$
(f) $\mathrm{FeSO}_{4} \cdot \mathrm{C}_{2} \mathrm{H}_{4}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{SO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}$

Ronald Prasad
Ronald Prasad
Numerade Educator
04:21

Problem 13

Calculate the number of grams of each of the substances in Problem 12 that would have to be dissolved and diluted to $100 \mathrm{~mL}$ to prepare a $0.200 \mathrm{M}$ solution.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
01:52

Problem 14

Calculate the number of milligrams of each of the following substances you would have to weigh out in order to prepare the listed solutions: (a) $1.00 \mathrm{~L}$ of $1.00 \mathrm{M} \mathrm{NaCl}$,
(b) $0.500 \mathrm{~L}$ of 0.200 $M$ sucrose $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right),$ (c) $10.0 \mathrm{~mL}$ of $0.500 \mathrm{M}$ sucrose, (d) $0.0100 \mathrm{~L}$ of $0.200 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4},$ (e)
$250 \mathrm{~mL}$ of $0.500 \mathrm{M} \mathrm{KOH},$ (f) $250 \mathrm{~mL}$ of $0.900 \% \mathrm{NaCl}(\mathrm{g} / 100 \mathrm{~mL}$ solution $)$

Lottie Adams
Lottie Adams
Numerade Educator
01:10

Problem 15

The chemical stockroom is supplied with the following stock solutions: $0.100 M \mathrm{HCl}$ $0.0200 \mathrm{M} \mathrm{NaOH}, 0.0500 \mathrm{M} \mathrm{KOH}, 10.0 \% \mathrm{HBr}(\mathrm{wt} / \mathrm{vol}),$ and $5.00 \% \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{wt} / \mathrm{vol}) .$ What volume of stock solution would be needed to obtain the following amounts of solutes? (a) $0.0500 \mathrm{~mol} \mathrm{HCl},$ (b) $0.0100 \mathrm{~mol} \mathrm{NaOH},(\mathrm{c}) 0.100 \mathrm{~mol} \mathrm{KOH}$ (d) $5.00 \mathrm{~g} \mathrm{HBr},$
(e) $4.00 \mathrm{~g} \mathrm{Na}_{2} \mathrm{CO}_{3}$ (f) $1.00 \mathrm{~mol} \mathrm{HBr},(\mathrm{g}) 0.500 \mathrm{~mol} \mathrm{Na}_{2} \mathrm{CO}_{3}$ -

Eileen Sullivan
Eileen Sullivan
Numerade Educator
02:20

Problem 16

Calculate the molar concentrations of all the cations and anions in a solution prepared by mixing $10.0 \mathrm{~mL}$ each of the following solutions: $0.100 \mathrm{M} \mathrm{Mn}\left(\mathrm{NO}_{3}\right)_{2}, 0.100 M \mathrm{KNO}_{3},$ and $0.100 M \mathrm{~K}, \mathrm{SO}_{4}$ \end{aligned}

Simon Kangoun
Simon Kangoun
Numerade Educator
01:58

Problem 17

A solution containing $10.0 \mathrm{mmol} \mathrm{CaCl}_{2}$ is diluted to $1 \mathrm{~L}$. Calculate the number of grams of $\mathrm{CaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ per milliliter of the final solution.

Shazia Naz
Shazia Naz
Numerade Educator
02:05

Problem 18

Calculate the molarity of each of the following solutions: (a) $10.0 \mathrm{~g} \mathrm{H}_{2} \mathrm{SO}_{4}$ in $250 \mathrm{~mL}$ of solution, (b) $6.00 \mathrm{~g} \mathrm{NaOH}$ in $500 \mathrm{~mL}$ of solution. (c) $25.0 \mathrm{~g} \mathrm{AgNO}_{3}$ in $1.00 \mathrm{~L}$ of solution.

John Nicolle
John Nicolle
Numerade Educator
04:00

Problem 19

Calculate the number of grams in $500 \mathrm{~mL}$ of each of the following solutions:
(a) $0.100 M$ $\mathrm{Na}_{2} \mathrm{SO}_{4},$ (b) $0.250 \mathrm{M} \mathrm{Fe}\left(\mathrm{NH}_{4}\right)_{2}\left(\mathrm{SO}_{4}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O},$ (c) $0.667 \mathrm{M} \mathrm{Ca}\left(\mathrm{C}_{9} \mathrm{H}_{6} \mathrm{ON}\right)_{2}$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:09

Problem 20

Calculate the grams of each substance required to prepare the following solutions:
(a) $250 \mathrm{~mL}$ of $0.100 M \mathrm{KOH}$ (b) $1.00 \mathrm{~L}$ of $0.0275 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7},$ (c) $500 \mathrm{~mL}$ of $0.0500 \mathrm{M} \mathrm{CuSO}_{4}$

David Collins
David Collins
Numerade Educator
03:23

Problem 21

How many milliliters of concentrated hydrochloric acid, $38.0 \%$ (wt/wt), specific gravity 1.19 , are required to prepare $1 \mathrm{~L}$ of a $0.100 \mathrm{M}$ solution? (Assume density and specific gravity are equal within three significant figures.)

Aadit Sharma
Aadit Sharma
Numerade Educator
07:50

Problem 22

Calculate the molarity of each of the following commercial acid or base solutions: (a) $70.0 \%$ $\mathrm{HClO}_{4},$ specific gravity $1.668,$ (b) $69.0 \% \mathrm{HNO}_{3},$ specific gravity $1.409,$ (c) $85.0 \% \mathrm{H}_{3} \mathrm{PO}_{4},$ specific gravity $1.689,$ (d) $99.5 \% \mathrm{CH}_{3} \mathrm{COOH}$ (acetic acid), specific gravity $1.051,$ (e) $28.0 \%$ $\mathrm{NH}_{3},$ specific gravity $0.898 .$ (Assume density and specific gravity are equal within three significant figures.)

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:12

Problem 23

A solution contains $6.0 \mu \mathrm{mol} \mathrm{Na}_{2} \mathrm{SO}_{4}$ in $250 \mathrm{~mL}$. How many $\mathrm{mg} / \mathrm{L}$ sodium does it contain? Of sulfate?

Zafar Haider
Zafar Haider
Numerade Educator
01:21

Problem 24

A solution ( $100 \mathrm{~mL}$ ) containing $325 \mathrm{mg} / \mathrm{L} \mathrm{K}^{+}$ is analyzed by precipitating it as the tetraphenyl borate, $\mathrm{K}\left(\mathrm{C}_{6} \mathrm{H}_{5}\right)_{4} \mathrm{~B},$ dissolving the precipitate in acetone solution, and measuring the concentration of tetraphenyl borate ion, $\left(\mathrm{C}_{6} \mathrm{H}_{5}\right)_{4} \mathrm{~B}^{-},$ in the solution. If the acetone solution volume is $250 \mathrm{~mL}$, what is the concentration of the tetraphenyl borate in $\mathrm{mg} / \mathrm{L} ?$

David Collins
David Collins
Numerade Educator
01:40

Problem 25

Calculate the molar concentrations of $1.00-\mathrm{mg} / \mathrm{L}$ solutions of each of the following. (a) $\mathrm{AgNO}_{3},$ (e) $\mathrm{HCl},$ (f) $\mathrm{HClO}_{4}$.
(b) $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3},$ (c) $\mathrm{CO}_{2},$ (d) $\left(\mathrm{NH}_{4}\right)_{4} \mathrm{Ce}\left(\mathrm{SO}_{4}\right)_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}$

Crystal Wang
Crystal Wang
Numerade Educator
02:20

Problem 26

Calculate the $\mathrm{mg} / \mathrm{L}$ concentrations of $2.50 \times 10^{-4} \mathrm{M}$ solutions of each of the following. (a) $\mathrm{Ca}^{2+},$ (b) $\mathrm{CaCl}_{2},$ (c) $\mathrm{HNO}_{3},$ (d) $\mathrm{KCN}$ (e) $\mathrm{Mn}^{2+},$ (f) $\mathrm{MnO}_{4}^{-}$.

Henry He
Henry He
Numerade Educator
04:16

Problem 27

You want to prepare $1 \mathrm{~L}$ of a solution containing $1.00 \mathrm{mg} / \mathrm{L} \mathrm{Fe}^{2+}$. How many grams ferrous ammonium sulfate, $\mathrm{FeSO}_{4} \cdot\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \cdot 6 \mathrm{H}_{2} \mathrm{O},$ must be dissolved and diluted in $1 \mathrm{~L} ?$ What would be the molarity of this solution?

Susan Hallstrom
Susan Hallstrom
Numerade Educator
01:58

Problem 28

A 0.456-g sample of an ore is analyzed for chromium and found to contain $0.560 \mathrm{mg} \mathrm{Cr}_{2} \mathrm{O}_{3}$. Express the concentration of $\mathrm{Cr}_{2} \mathrm{O}_{3}$ in the sample as (a) percent, (b) parts per thousand, and (c) parts per million.

Ronald Prasad
Ronald Prasad
Numerade Educator
01:20

Problem 29

How many grams $\mathrm{NaCl}$ should be weighed out to prepare $1 \mathrm{~L}$ of a $100-\mathrm{mg} / \mathrm{L}$ solution of (a) $\mathrm{Na}^{+}$ and (b) $\mathrm{Cl}^{-} ?$

Lottie Adams
Lottie Adams
Numerade Educator
03:00

Problem 30

You have a $250-\mathrm{mg} / \mathrm{L}$ solution of $\mathrm{K}^{+}$ as $\mathrm{KCl}$. You wish to prepare from this a $0.00100 \mathrm{M}$ solution of $\mathrm{Cl}^{-}$. How many milliliters must be diluted to $1 \mathrm{~L}$ ?

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:08

Problem 31

One liter of a $500-\mathrm{mg} / \mathrm{L}$ solution of $\mathrm{KClO}_{3}$ contains how many grams $\mathrm{K}^{+} ?$

Cheryl Glor
Cheryl Glor
Numerade Educator
01:45

Problem 32

A $12.5-\mathrm{mL}$ portion of a solution is diluted to $500 \mathrm{~mL}$, and its molarity is determined to be $0.125 .$ What is the molarity of the original solution?

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
00:24

Problem 33

What volume of $0.50 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ must be added to $65 \mathrm{~mL}$ of $0.20 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ to give a final solution of $0.35 M ?$ Assume volumes are additive.

David Collins
David Collins
Numerade Educator
02:01

Problem 34

How many milliliters of $0.10 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ must be added to $50 \mathrm{~mL}$ of $0.10 \mathrm{M} \mathrm{NaOH}$ to give a solution that is $0.050 \mathrm{M}$ in $\mathrm{H}_{2} \mathrm{SO}_{4}$ ? Assume volumes are additive.

Ramesh Singh
Ramesh Singh
Numerade Educator
02:51

Problem 35

You are required to prepare working standard solutions of $1.00 \times 10^{-5}, 2.00 \times 10^{-5}, 5.00 \times$ $10^{-5}$, and $1.00 \times 10^{-4} M$ glucose from a $0.100 \mathrm{M}$ stock solution. You have available $100-\mathrm{mL}$ volumetric flasks and pipets of $1.00-, 2.00-, 5.00-,$ and $10.00-\mathrm{mL}$ volume. Outline a procedure for preparing the working standards.

Freddie Montague
Freddie Montague
Numerade Educator
03:31

Problem 36

A $0.500-\mathrm{g}$ sample is analyzed spectrophotometrically for manganese by dissolving it in acid and transferring to a $250-\mathrm{mL}$ flask and diluting to volume. Three aliquots are analyzed by transferring $50-\mathrm{mL}$ portions with a pipet to $500-\mathrm{mL}$ Erlenmeyer flasks and reacting with an oxidizing agent, potassium peroxydisulfate, to convert the manganese to permanganate. After reaction, these are quantitatively transferred to $250-\mathrm{mL}$ volumetric flasks, diluted to volume, and measured spectrophotometrically. By comparison with standards, the average concentration in the final solution is determined to be $1.25 \times 10^{-5} M .$ What is the percent manganese in the sample?

Zafar Haider
Zafar Haider
Numerade Educator
07:57

Problem 37

A stock solution of analyte is made by dissolving $34.83 \mathrm{mg}$ of copper (II) acetate hexahydrate (fw $=289.73 \mathrm{~g} / \mathrm{mol}$ ) in $25.00 \mathrm{~mL}$ of water. A second stock solution of internal standard is made by dissolving $28.43 \mathrm{mg}$ of germanium (I) acetate $(\mathrm{fw}=190.74 \mathrm{~g} / \mathrm{mol}$ ) into $25.00 \mathrm{~mL}$ of water. These solutions are used to make a series of standards for flame atomic absorption analysis calibration. The standard solutions (each $10.00 \mathrm{~mL}$ total volume) should have the following concentrations of copper: $10.00 ; 25.00 ; 50.00 ; 100.0 ;$ and $200.0 \mu \mathrm{M}$. Each calibration solution should also contain $50.00 \mu \mathrm{M}$ of germanium.

Iva Lazarova
Iva Lazarova
Numerade Educator
02:53

Problem 38

Tom, an analytical chemist, bought a bag of decaffeinated coffee from a grocery store. However, Tom suspected that he might have received regular coffee and therefore decided to analyze his coffee for caffeine. In the lab, he took $0.5 \mathrm{~mL}$ of the brewed coffee and diluted it in water to make a $100.0 \mathrm{~mL}$ solution. He performed four analyses and found the concentrations to be $4.69,$ $3.99,4.12,$ and $4.50 \mathrm{mg} / \mathrm{L},$ respectively. (Assume the density of all solutions is $1.000 \mathrm{~g} / \mathrm{mL}$ $1 \mathrm{oz}=28.35 \mathrm{~mL})$
(a) Report the concentration (in $\mathrm{mg} / \mathrm{L}$ ) of caffeine in the brewed coffee using the format as average $\pm$ standard deviation. (Note this is not the concentration in the diluted solution.)
(b) Look up the caffeine content of regular vs. decaffeinated coffee. Do you think that Tom was given the wrong type of coffee?
(c) Caffeine intake of $300 \mathrm{mg}$ per day reportedly has no adverse effects in the vast majority of the adult population. If Tom drinks 3 cups ( 8 oz/cup) of this coffee daily, is his intake within this known safe zone?

Lucas Finney
Lucas Finney
Numerade Educator
02:00

Problem 39

A preparation of soda ash is known to contain $98.6 \% \mathrm{Na}_{2} \mathrm{CO}_{3} .$ If a $0.678-\mathrm{g}$ sample requires $36.8 \mathrm{~mL}$ of a sulfuric acid solution for complete neutralization, what is the molarity of the sulfuric acid solution?

Ronald Prasad
Ronald Prasad
Numerade Educator
08:34

Problem 40

A $0.1 M$ sodium hydroxide solution is to be standardized by titrating primary standard sulfamic acid $\left(\mathrm{NH}_{2} \mathrm{SO}_{3} \mathrm{H}\right)$. What weight of sulfamic acid should be taken so that the volume of $\mathrm{NaOH}$ delivered from the buret is about $40 \mathrm{~mL} ?$

Marietjie Lutz
Marietjie Lutz
Numerade Educator
02:30

Problem 41

A sample of USP-grade citric acid $\left(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7},\right.$ three titratable protons) is analyzed by titrating with $0.1087 M \mathrm{NaOH}$. If a $0.2678-\mathrm{g}$ sample requires $38.31 \mathrm{~mL}$ for titration, what is the purity of the preparation? USP specification requires $99.5 \%$.

Banhishikha Sinha
Banhishikha Sinha
Numerade Educator
01:45

Problem 42

Calcium in a $200-\mu \mathrm{L}$ serum sample is titrated with $1.87 \times 10^{-4} M$ EDTA solution, requiring $2.47 \mathrm{~mL}$. What is the calcium concentration in the blood in $\mathrm{mg} / \mathrm{dL} ?$

David Collins
David Collins
Numerade Educator
08:46

Problem 43

A $0.372-\mathrm{g}$ sample of impure $\mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ is titrated with $0.100 \mathrm{M} \mathrm{AgNO}_{3}$, requiring $27.2 \mathrm{~mL}$. Calculate (a) the percent $\mathrm{Cl}$ in the sample and (b) the percent purity of the compound.

Anna D.
Anna D.
Numerade Educator
06:03

Problem 44

An iron ore is analyzed for iron content by dissolving in acid, converting the iron to $\mathrm{Fe}^{2+},$ and then titrating with standard $0.0150 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ solution. If $35.6 \mathrm{~mL}$ is required to titrate the iron in a $1.68-\mathrm{g}$ ore sample, how much iron is in the sample, expressed as percent $\mathrm{Fe}_{2} \mathrm{O}_{3} ?$ (See Example 5.31 for the titration reaction.)

Kim Trang Nguyen
Kim Trang Nguyen
Numerade Educator
02:30

Problem 45

Calcium in a $2.00-\mathrm{g}$ sample is determined by precipitating $\mathrm{CaC}_{2} \mathrm{O}_{4},$ dissolving this in acid, and titrating the oxalate with $0.0200 \mathrm{M} \mathrm{KMnO}_{4} .$ What percent of $\mathrm{CaO}$ is in the sample if $35.6 \mathrm{~mL} \mathrm{KMnO}_{4}$ is required for titration? (The reaction is $5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}+2 \mathrm{MnO}_{4}^{-}+6 \mathrm{H}^{+} \rightarrow$
$10 \mathrm{CO}_{2}+2 \mathrm{Mn}^{2+}+8 \mathrm{H}_{2} \mathrm{O} .$

Crystal Wang
Crystal Wang
Numerade Educator
03:31

Problem 46

A potassium permanganate solution is prepared by dissolving $4.68 \mathrm{~g} \mathrm{KMnO}_{4}$ in water and diluting to $500 \mathrm{~mL}$. How many milliliters of this will react with the iron in $0.500 \mathrm{~g}$ of an ore containing $35.6 \% \mathrm{Fe}_{2} \mathrm{O}_{3}$?

Zafar Haider
Zafar Haider
Numerade Educator
08:46

Problem 47

A sample contains $\mathrm{BaCl}_{2}$ plus inert matter. What weight must be taken so that when the solution is titrated with $0.100 \mathrm{AgNO}_{3}$, the milliliters of titrant will be equal to the percent $\mathrm{BaCl}_{2}$ in the sample?

Anna D.
Anna D.
Numerade Educator
06:30

Problem 48

A $0.250-\mathrm{g}$ sample of impure $\mathrm{AlCl}_{3}$ is titrated with $0.100 \mathrm{M} \mathrm{AgNO}_{3},$ requiring $48.6 \mathrm{~mL}$. What volume of $0.100 \mathrm{M}$ EDTA would react with a $0.350-\mathrm{g}$ sample? (EDTA reacts with $\mathrm{Al}^{3+}$ in a 1: 1 ratio.)

Susan Hallstrom
Susan Hallstrom
Numerade Educator
02:16

Problem 49

A 425.2-mg sample of a purified monoprotic organic acid is titrated with $0.1027 M \mathrm{NaOH}$, requiring $28.78 \mathrm{~mL}$. What is the formula weight of the acid?

Ronald Prasad
Ronald Prasad
Numerade Educator
07:04

Problem 50

The purity of a 0.287 -g sample of $\mathrm{Zn}(\mathrm{OH})_{2}$ is determined by titrating with a standard $\mathrm{HCl}$ solution, requiring $37.8 \mathrm{~mL}$. The HCl solution was standardized by precipitating $\mathrm{AgCl}$ in a $25.0-\mathrm{mL}$ aliquot and weighing $(0.462 \mathrm{~g} \mathrm{AgCl}$ obtained $) .$ What is the purity of the $\mathrm{Zn}(\mathrm{OH})_{2} ?$

Md Mohibullah
Md Mohibullah
Auburn University Main Campus
01:46

Problem 51

A sample of pure $\mathrm{KHC}_{2} \mathrm{O}_{4} \cdot \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ (three replaceable hydrogens) requires $46.2 \mathrm{~mL}$ of $0.100 \mathrm{M} \mathrm{NaOH}$ for titration. How many milliliters of $0.100 \mathrm{M} \mathrm{KMnO}_{4}$ will the same-size sample react with? (See Problem 45 for reaction with $\mathrm{KMnO}_{4}$.)

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
03:23

Problem 52

A $0.500-g$ sample containing $\mathrm{Na}_{2} \mathrm{CO}_{3}$ plus inert matter is analyzed by adding $50.0 \mathrm{~mL}$ of $0.100 M \mathrm{HCl}$, a slight excess, boiling to remove $\mathrm{CO}_{2}$, and then back-titrating the excess acid with $0.100 \mathrm{M} \mathrm{NaOH}$. If $5.6 \mathrm{~mL}$ NaOH is required for the back-titration, what is the percent $\mathrm{Na}_{2} \mathrm{CO}_{3}$ in the sample?

David Collins
David Collins
Numerade Educator
02:31

Problem 53

A hydrogen peroxide solution is analyzed by adding a slight excess of standard $\mathrm{KMnO}_{4}$ solution and back-titrating the unreacted $\mathrm{KMnO}_{4}$ with standard $\mathrm{Fe}^{2+}$ solution. A $0.587-\mathrm{g}$ sample of the $\mathrm{H}_{2} \mathrm{O}_{2}$ solution is taken, $25.0 \mathrm{~mL}$ of $0.0215 \mathrm{M} \mathrm{KMnO}_{4}$ is added, and the back-titration requires $5.10 \mathrm{~mL}$ of $0.112 \mathrm{M} \mathrm{Fe}^{2+}$ solution. What is the percent $\mathrm{H}_{2} \mathrm{O}_{2}$ in the sample? (See Examples 5.26 and 5.30 for the reactions.)

Bhumika Jayee
Bhumika Jayee
Numerade Educator
01:26

Problem 54

The sulfur content of an iron pyrite ore sample is determined by converting it to $\mathrm{H}_{2} \mathrm{~S}$ gas, absorbing the $\mathrm{H}_{2} \mathrm{~S}$ in $10.0 \mathrm{~mL}$ of $0.00500 \mathrm{M} \mathrm{I}_{2},$ and then back-titrating the excess $\mathrm{I}_{2}$ with $0.00200 \mathrm{M} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} .$ If $2.6 \mathrm{~mL} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ is required for the titration, how many milligrams of sulfur are contained in the sample? Reactions:
$$
\begin{aligned}
\mathrm{H}_{2} \mathrm{~S}+\mathrm{I}_{2} \rightarrow \mathrm{S}+2 \mathrm{I}^{-}+2 \mathrm{H}^{+} \\
\mathrm{I}_{2}+2 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-} \rightarrow 2 \mathrm{I}^{-}+\mathrm{S}_{4} \mathrm{O}_{6}^{2-}
\end{aligned}
$$

Lottie Adams
Lottie Adams
Numerade Educator
01:45

Problem 55

Express the titer of a $0.100 M$ EDTA solution in $\mathrm{mg} \mathrm{BaO} / \mathrm{mL}$.

David Collins
David Collins
Numerade Educator
02:33

Problem 56

Express the titer of a $0.0500 \mathrm{M} \mathrm{KMnO}_{4}$ solution in $\mathrm{mg} \mathrm{Fe}_{2} \mathrm{O}_{3} / \mathrm{mL}$

Angelina Chavez
Angelina Chavez
Numerade Educator
01:06

Problem 57

The titer of a silver nitrate solution is $22.7 \mathrm{mg} \mathrm{Cl} / \mathrm{mL}$. What is its titer in $\mathrm{mg} \mathrm{Br} / \mathrm{mL} ?$

David Collins
David Collins
Numerade Educator
01:19

Problem 58

Calculate the equivalent weights of the following substances as acids or bases:
(a) $\mathrm{HCl},$
(b) $\mathrm{Ba}(\mathrm{OH})_{2},$
(c) $\mathrm{KH}\left(\mathrm{IO}_{3}\right)_{2}$,
(d) $\mathrm{H}_{2} \mathrm{SO}_{3}$
(e) $\mathrm{CH}_{3} \mathrm{COOH}$.

Shveta Prithiani
Shveta Prithiani
Numerade Educator
07:51

Problem 59

Calculate the molarity of a 0.250 eq/L solution of each of the acids or bases in Problem 58 .

Freddie Montague
Freddie Montague
Numerade Educator
05:01

Problem 60

Calculate the equivalent weight of $\mathrm{KHC}_{2} \mathrm{O}_{4}$ (a) as an acid and (b) as a reducing agent in reaction with $\mathrm{MnO}_{4}^{-}\left(5 \mathrm{HC}_{2} \mathrm{O}_{4}^{-}+2 \mathrm{MnO}_{4}^{-}+11 \mathrm{H}^{+} \rightarrow 10 \mathrm{CO}_{2}+2 \mathrm{Mn}^{2+}+8 \mathrm{H}_{2} \mathrm{O}\right)$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
01:54

Problem 61

Mercuric oxide, $\mathrm{HgO}$, can be analyzed by reaction with iodide and then titration with an acid:
$\mathrm{HgO}+4 \mathrm{I}^{-} \rightarrow \mathrm{Hgl}_{4}^{2-}+2 \mathrm{OH}^{-} .$ What is its equivalent weight?

Lottie Adams
Lottie Adams
Numerade Educator
05:59

Problem 62

Calculate the grams of one equivalent each of the following for the indicated reaction:
(a) $\mathrm{FeSO}_{4}\left(\mathrm{Fe}^{2+} \rightarrow \mathrm{Fe}^{3+}\right)$
(b) $\mathrm{H}_{2} \mathrm{~S}\left(\rightarrow \mathrm{S}^{0}\right)$
(c) $\mathrm{H}_{2} \mathrm{O}_{2}\left(\rightarrow \mathrm{O}_{2}\right)$
(d) $\mathrm{H}_{2} \mathrm{O}_{2}\left(\rightarrow \mathrm{H}_{2} \mathrm{O}\right)$

Cheryl Glor
Cheryl Glor
Numerade Educator
03:35

Problem 63

$\mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ is to be used to titrate $\mathrm{Ag}^{+}$ to yield $\mathrm{AgCl}$. How many milliequivalents are contained in $0.5000 \mathrm{~g} \mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$?

Nicholas Mogoi
Nicholas Mogoi
Numerade Educator
03:55

Problem 64

A solution is prepared by dissolving $7.82 \mathrm{~g} \mathrm{NaOH}$ and $9.26 \mathrm{~g} \mathrm{Ba}(\mathrm{OH})_{2}$ in water and diluting to $500 \mathrm{~mL}$. What is the concentration of the solution as a base in eq/L?

Zafar Haider
Zafar Haider
Numerade Educator
02:44

Problem 65

What weight of arsenic trioxide, $\mathrm{As}_{2} \mathrm{O}_{3},$ is required to prepare $1 \mathrm{~L}$ of $0.1000 \mathrm{eq} / \mathrm{L}$ arsenic(III) solution (arsenic $\mathrm{As}^{3+}$ is oxidized to $\mathrm{As}^{5+}$ in redox reactions)?

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:19

Problem 66

If $2.73 \mathrm{~g} \mathrm{KHC}_{2} \mathrm{O}_{4} \cdot \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}$ (three ionizable protons) having $2.0 \%$ inert impurities and $1.68 \mathrm{~g}$
$\mathrm{KHC}_{8} \mathrm{H}_{4} \mathrm{O}_{4}$ (one ionizable proton) are dissolved in water and diluted to $250 \mathrm{~mL}$, what is the concentration of the solution as an acid in eq/L, assuming complete ionization?

Ronald Prasad
Ronald Prasad
Numerade Educator
01:09

Problem 67

A solution of $\mathrm{KHC}_{2} \mathrm{O}_{4} \cdot \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ (three replaceable hydrogens) is $0.200 \mathrm{eq} / \mathrm{L}$ as an acid. What is its concentration in eq/L as reducing agent? (See Problem 45 for its reaction as a reducing agent.)

Adriano Chikande
Adriano Chikande
Numerade Educator
03:37

Problem 68

$\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}$ and $\mathrm{KHC}_{2} \mathrm{O}_{4} \cdot \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}$ are mixed in such a proportion by weight that the concentration of the resulting solution as a reducing agent in eq/L is 3.62 times the concentration as an acid in eq/L. What is the proportion? (See Problem 45 for its reaction as a reducing agent.)

Daniel Kyinakwa
Daniel Kyinakwa
Numerade Educator
02:37

Problem 69

What weight of $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ is required to prepare $1.000 \mathrm{~L}$ of $0.1000 \mathrm{eq} / \mathrm{L}$ solution? (It reacts as:
$\left.\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightleftharpoons 2 \mathrm{Cr}^{3}+7 \mathrm{H}_{2} \mathrm{O} .\right)$

Anatole Borisov
Anatole Borisov
Numerade Educator
03:57

Problem 70

A chloride concentration is reported as $300 \mathrm{mg} / \mathrm{dL}$. What is the concentration in meq/L?

Zafar Haider
Zafar Haider
Numerade Educator
03:05

Problem 71

A calcium concentration is reported as $5.00 \mathrm{meq} / \mathrm{L}$. What is the concentration in $\mathrm{mg} / \mathrm{dL} ?$

Isabella Huang
Isabella Huang
Numerade Educator
04:35

Problem 72

A urine specimen has a chloride concentration of $150 \mathrm{meq} / \mathrm{L}$. If we assume that the chloride is present in urine as sodium chloride, what is the concentration of $\mathrm{NaCl}$ in $\mathrm{g} / \mathrm{L} ?$

Christopher Nilsen
Christopher Nilsen
Numerade Educator
03:49

Problem 73

What weight of manganese is present in $2.58 \mathrm{~g}$ of $\mathrm{Mn}_{3} \mathrm{O}_{4} ?$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:14

Problem 74

Zinc is determined by precipitating and weighing as $\mathrm{Zn}_{2} \mathrm{Fe}(\mathrm{CN})_{6}$
(a) What weight of zinc is contained in a sample that gives 0.348 g precipitate?
(b) What weight of precipitate would be formed from $0.500 \mathrm{~g}$ of zinc?

Narayan Hari
Narayan Hari
Numerade Educator
03:44

Problem 75

Calculate the gravimetric factors for:
$$
\begin{array}{cc}
\hline \text { Substance Sought } & \text { Substance Weighed } \\
\hline \mathrm{Mn} & \mathrm{Mn}_{3} \mathrm{O}_{4} \\
\mathrm{Mn}_{2} \mathrm{O}_{3} & \mathrm{Mn}_{3} \mathrm{O}_{4} \\
\mathrm{Ag}_{2} \mathrm{~S} & \mathrm{BaSO}_{4} \\
\mathrm{CuCl}_{2} & \mathrm{AgCl} \\
\mathrm{MgI}_{2} & \mathrm{PbI}_{2} \\
\hline
\end{array}
$$

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:50

Problem 76

A $10.00 \mathrm{~g}$ sample contains only $\mathrm{NaCl}$ and $\mathrm{KCl}$. The sample is dissolved and $\mathrm{AgNO}_{3}$ is added to precipitate AgCl. After the precipitate is washed and dried, it weighs $21.62 \mathrm{~g}$. What is the weight percent of $\mathrm{NaCl}$ in the original sample?

David Collins
David Collins
Numerade Educator