Question 1

What is the formula mass of aluminum sulfate, $$\mathrm{Al_2$(SO_4$)_3}$$, based on the data provided in the image?

Accepted Answer

$$\mathrm{342.14\ amu}$$

Question 2

A compound contains 1.71 g of carbon and 0.287 g of hydrogen. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH}$$

Question 3

A 0.00126-g sample of polyethylene yields 0.00394 g of $$\mathrm{CO_2$}$$ and 0.00161 g of $$\mathrm{H_2O}$$ upon combustion. What is the empirical formula of polyethylene?

Accepted Answer

$$\mathrm{CH_2$}$$

Question 4

Which of the following best describes the process shown in the image with a spoon adding sugar to a cup of coffee?

Accepted Answer

Preparation of a solution by dissolving a solute in a solvent

Question 5

A solution is prepared by dissolving 10.0 g of NaCl in enough water to make 500 mL of solution. What is the molarity of the solution? ($$\mathrm{M_{NaCl} = 58.44\ g/mol})$$

Accepted Answer

$$0.171\ \mathrm{M}$$

Question 6

Which equation correctly relates the molarity and volume of a solution before and after dilution?

Accepted Answer

$$M_1V_1 = M_2V_2$$

Question 7

A bleach solution contains 7.4% NaOCl by mass. If you have 250 g of this solution, how many grams of NaOCl are present?

Accepted Answer

$$18.5\ \mathrm{g}$$

Question 8

Which of the following best describes the role of the furnace in the combustion analysis apparatus shown in the image?

Accepted Answer

It provides the high temperature needed for complete combustion of the sample

Question 9

A solution is labeled as 0.9% (m/v) NaCl. How many grams of NaCl are present in 250 mL of this solution?

Accepted Answer

$$2.25\ \mathrm{g}$$

Question 10

A compound has an empirical formula of $$\mathrm{CH_2O}$$ and a molar mass of 180 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$}$$

Question 11

Which of the following is the correct sequence of steps to determine the empirical formula from mass data, as shown in the flowchart?

Accepted Answer

Convert mass to moles, divide by smallest number of moles, convert to whole numbers

Question 12

A 355 mL bottle of rubbing alcohol is labeled as 70% by volume isopropanol. How many mL of isopropanol are present?

Accepted Answer

$$248.5\ \mathrm{mL}$$

Question 13

If a solution contains 15 ppb of lead, what is this concentration in ppm?

Accepted Answer

$$0.015\ \mathrm{ppm}$$

Question 14

Which of the following statements is true regarding the difference between formula mass and molecular mass?

Accepted Answer

Formula mass is used for ionic compounds, while molecular mass is used for covalent compounds.

Question 15

A solution is prepared by diluting 50.0 mL of 6.0 M HCl to a final volume of 300.0 mL. What is the final concentration?

Accepted Answer

$$1.0\ \mathrm{M}$$

Question 16

Which of the following best describes the term 'solute' in a solution?

Accepted Answer

The component present in a smaller amount, which is dissolved in the solvent

Composition of Substances and Solutions: Formula Mass, Empirical Formulas, and Solution Concentrations

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