Calculate the molarities of solutions that contain the...

Calculate the molarities of solutions that contain the following masses of solute in the indicated volumes: (a) $35.5 \mathrm{~g}$ of $\mathrm{H}_{3} \mathrm{AsO}_{4}$ in $500 . \mathrm{mL}$ of solution; (b) $8.33 \mathrm{~g}$ of $(\mathrm{COOH})_{2}$ in $600 . \mathrm{mL}$ of solution; $(\mathrm{c}) 8.25 \mathrm{~g}$ of $(\mathrm{COOH})_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ in $750 . \mathrm{mL}$ of solution.

Calculate the molarities of solutions that contain the following masses of solute in the indicated volumes:
(a) $35.5 \mathrm{~g}$ of $\mathrm{H}_{3} \mathrm{AsO}_{4}$ in $500 . \mathrm{mL}$ of solution; (b) $8.33 \mathrm{~g}$ of $(\mathrm{COOH})_{2}$ in $600 . \mathrm{mL}$ of solution; $(\mathrm{c}) 8.25 \mathrm{~g}$ of $(\mathrm{COOH})_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ in $750 . \mathrm{mL}$ of solution.

Key Concepts

Molarity

Molarity is a measure of concentration expressed in moles of solute per liter of solution. It quantifies how much solute is present in a given volume of solvent and is essential for preparing and analyzing chemical solutions.

Moles

The mole is a fundamental unit in chemistry used to count particles, defined as the amount of substance containing the same number of discrete entities as there are atoms in 12 grams of carbon-12. It allows conversion between the mass of a substance and the number of entities using its molar mass.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). This value is obtained by summing the atomic masses of all atoms in the compound's formula and is crucial for converting between mass and moles.

Volume Conversion

In concentration calculations, especially for molarity, it is important to convert the volume of a solution to liters if it is given in another unit like milliliters. This standardization ensures that the molarity is correctly calculated as moles per liter.

Conversion from Grams to Moles

This key calculation involves determining the number of moles by dividing the mass of a substance by its molar mass. This conversion is a fundamental step when calculating concentrations and performing stoichiometric computations in chemical reactions.

Transcript

00:01 In this question, we need to determine the mularity of different solutions containing specific masses of solute, and we're working with specific volumes of solution that is provided alongside with the masses of the solute.

00:18 Now, we know that molarity is calculated in terms of moles per liter.

00:25 So therefore, we need to make sure that we have the number of moles in each of these cases.

00:30 And we're working with liters.

00:34 Now in the first part of the question, part a, we need to calculate the molarity of arsenic acid.

00:43 The mass of arsenic acid is given as 35 .5 grams.

00:48 I've pre -calculated the molar mass of arsenic acid as we need to use this in order to determine the number of moles of arsenic acid.

01:00 The volume of a scenic acid or the volume of the solution that we're working with is given as 500 milliliters.

01:09 So we need to convert that to liters.

01:13 So that's 0 .5 .0 .50 liters.

01:23 And therefore, we can say that the molarity will then be, we're going to take the mass.

01:30 Of 35 .5 grams of arsenic acid.

01:37 And we can multiply that with the inverse of the molar mass of arsenic acid.

01:45 Because the molar mass of arsenic acid is in terms of grams per mole.

01:51 But now we want to get rid of the number of grams.

01:54 So we're going to say it's one mole per.

02:02 Over 141 .9 grams of arsenic acid.

02:08 So just repeating that, the molar mass of arsenic acid is 1419, 1 .4 .1 .9 grams per one mole of arsenic acid.

02:21 But we're going to work with the inverse of the molar mass in order to get rid of the grams.

02:32 And then we need to divide by the volume.

02:36 So i'm just going to multiply by one over the volume.

02:42 So the volume we said in terms of liters 0 .5 .0...

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