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Composition

In pure or chemical compounds, the ratio of different atoms or molecules (e.g., the proportions of hydrogen and oxygen in water) is called the composition. The composition of a compound is usually described by the proportion of atoms of each element in the compound. The ratio may be expressed in any of several forms, including mass fraction (also called mole fraction), mole percentages, or weight percentages. The formula for the mass of a compound is a formula containing numeric quantities that shows the composition. For example, oxygen gas would have a mass formula of O. In chemical nomenclature, the term "composition" has two different meanings. In one use, it refers to the proportion of each element in a compound, as either a mass or a mole fraction. In the second use, it refers to the proportion of the different functional groups in a compound, as a percent by weight.

Formula Mass

76 Practice Problems
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02:21
Introduction to General, Organic and Biochemistry

Write the formulas of compounds in which the combining ratios are as follows:
(a) Potassium:oxygen, 2: 1
(b) Sodium:phosphorus: oxygen, 3: 1: 4
(c) Lithium:nitrogen: oxygen, 1: 1: 3

Atoms
Niamat Khuda
04:42
Chemistry

Calculate the molecular mass or formula mass (in amu) of each of the following substances: $(\mathrm{a}) \mathrm{Li}_{2} \mathrm{CO}_{3},(\mathrm{b}) \mathrm{C}_{2} \mathrm{H}_{6},(\mathrm{c}) \mathrm{NF}_{2}$
(d) $\mathrm{Al}_{2} \mathrm{O}_{3},(\mathrm{e}) \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3},(\mathrm{f}) \mathrm{PCl}_{5},(\mathrm{g}) \mathrm{Mg}_{3} \mathrm{N}_{2}$.

Stoichiometry: Ratios of Combination
Daniel Kim
02:00
General Chemistry: Principles and Modern Applications

Show that the empirical formula given for crysotile asbestos is consistent with the expected oxidation states of the elements present.

Chemistry of the Main-Group Elements I: Groups 1, 2, 13, and 14
Lottie Adams

Avogadro’s Number and Mole Concept

107 Practice Problems
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04:17
Introduction to General, Organic and Biochemistry

How many moles of lactate are produced from 3 moles of glucose?

Specific Catabolic Pathways: Carbohydrate, Lipid, and Protein Metabolism
Kadry Samuels
07:35
Introduction to General, Organic and Biochemistry

Furan, an organic compound used in the synthesis of nylon and referenced in Section $19.2,$ has the molecular formula $\mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}$
(a) Determine the number of moles of furan in a $441 \mathrm{mg}$ sample
(b) If the density of furan is known to be $0.936 \mathrm{g} / \mathrm{mL}$, how many carbon atoms are present in $0.060 \mathrm{L}$ of furan?
(c) Calculate the mass in grams of $9.86 \times 10^{25}$ molecules of furan.

Chemical Reactions and Energy Calculations
Carlene Jimenez
01:45
Introduction to General, Organic and Biochemistry

Refer to Figure $5-19 .$ How many calories are required to bring one mole of ice at $0^{\circ} \mathrm{C}$ to a liquid state at room temperature $\left(23^{\circ} \mathrm{C}\right) ?$

Gases, Liquids, and Solids
David Collins

Empirical and Molecular Formulas

178 Practice Problems
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06:57
Introduction to General, Organic and Biochemistry

What are the similarities and differences in the electron configurations of:
(a) Na and Cs?
(b) $\mathrm{O}$ and Te?
(c) $\mathrm{C}$ and Ge?

Atoms
Niamat Khuda
01:07
Introduction to General, Organic and Biochemistry

Write the formula for the most stable ion formed by each element.
(a) Mg
(b) F
(c) A
(d) S
{e} K
(f) Br

Chemical Bonds
Lottie Adams
02:33
Introduction to General, Organic and Biochemistry

Write the formulas of compounds in which the combining ratios are as follows:
(a) Sodium: chlorine: oxygen, 1: 1: 3
(b) Aluminum (atomic symbol Al): fluorine (atomic symbol $\mathrm{F}$ ), 1: 3

Atoms
Dr.  Satish  Ingale

Molarity

183 Practice Problems
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03:21
Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Write the rate equation for the following elementary reactions and give the molecularity for each reaction. (Sections 9.4 and 9.8)
(a) $\mathrm{Cr}+\mathrm{O}_{3} \rightarrow \mathrm{ClO}^{*}+\mathrm{O}_{2}$
(b) $\mathrm{CH}_{3} \mathrm{N}_{2} \mathrm{CH}_{3} \rightarrow 2 \mathrm{CH}_{3}^{*}+\mathrm{N}_{2}$
(c) $2 \mathrm{Cl}^{\prime} \rightarrow \mathrm{Cl}_{2}$
(d) $\mathrm{NO}_{2}^{*}+\mathrm{F}_{2} \rightarrow \mathrm{NO}_{2} \mathrm{F}+\mathrm{F}$

Reaction kinetics
Lottie Adams
07:45
Biochemistry

If you have $100 \mathrm{mL}$ of a $0.10 \mathrm{M}$ TRIS buffer at $\mathrm{pH} 8.3 \text { (Table } 2.8)$ and you add $3.0 \mathrm{mL}$ of $1 \mathrm{MHCl}$, what will be the new pH?

Water: The Solvent for Biochemical Reactions
Rachel Vallejo
01:05
Introduction to General, Organic and Biochemistry

What is the pH of each solution given the following values of $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right] ?$ Which solutions are acidic, which are basic, and which are neutral?
(a) $10^{-8} M$
(b) $10^{-10} M$
(c) $10^{-2} M$
(d) $10^{0} M$
$(e) 10^{-7} M$

Acids and Bases
David Collins

Concentration Units

165 Practice Problems
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02:13
Chemistry: Introducing Inorganic, Organic and Physical Chemistry

A sealed flask holds $10 \mathrm{dm}^{3}$ of gas. What is this volume in
(a) $\left.\mathrm{cm}^{3},(\mathrm{b}) \mathrm{m}^{3}, \text { (c) litres? (Section } 1.2\right)$

Fundamentals
Nicole Smina
01:36
Biochemistry

Define buffering capacity. How do the following buffers differ in buffering capacity? How do they differ in pH?
Buffer a: $0.01 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $0.01 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$
Buffer b: $0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $0.10 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$
Buffer $c: 1.0 M \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $1.0 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$

Water: The Solvent for Biochemical Reactions
Rachel Vallejo
01:21
Introduction to General, Organic and Biochemistry

What is the equilibrium constant for the following reaction? Equilibrium concentrations are given under the formula of each component.
$$\mathrm{PCl}_{3}+\mathrm{Cl}_{2} \rightleftharpoons \mathrm{PCl}_{5}$$

Reaction Rates and Chemical Equilibrium
David Collins

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