Q: Which of the following is the correct formula for calculating molarity ($$M$$)?

$$M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}$$

Q: Which of the following is the correct conversion factor to determine the number of molecules in 2.00 moles of $$\mathrm{H}_2\mathrm{O}$$?

$$2.00\ \mathrm{mol} \times 6.022 \times 10$$^{23}$$\ \mathrm{molecules/mol}$$

Question 1

Which of the following best describes the term 'empirical formula' in chemistry?

Accepted Answer

The formula showing the simplest whole-number ratio of atoms of each element in a compound.

Question 2

A compound contains 40.00% carbon, 6.67% hydrogen, and 53.33% oxygen by mass. What is the empirical formula of this compound?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 3

Which of the following is the correct calculation for the number of moles in 18.016 g of water ($$\mathrm{H}_2\mathrm{O}$$)?

Accepted Answer

$$\frac{18.016\ \mathrm{g}}{18.016\ \mathrm{g/mol}}$$

Question 4

A solution is prepared by dissolving 5.00 moles of NaCl in enough water to make 2.00 L of solution. What is the molarity ($$M) of $$the solution?

Accepted Answer

$$2.50\ M$$

Question 5

Which of the following statements about solutions is correct?

Accepted Answer

The solute is the substance being dissolved, and the solvent is the substance doing the dissolving.

Question 6

A student wants to prepare 250 mL of a 0.20 M NaOH solution. How many moles of NaOH are required?

Accepted Answer

$$0.050\ \mathrm{mol}$$

Question 7

Which of the following best describes a concentrated solution?

Accepted Answer

A solution with a large amount of solute relative to solvent.

Question 8

If you dilute 100 mL of a 1.0 M HCl solution to a final volume of 500 mL, what is the new concentration?

Accepted Answer

$$0.20\ M$$

Question 9

Which of the following is the correct formula for calculating molarity ($$M$$)?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{volume of solution in liters}}$$

Question 10

A compound has an empirical formula of $$\mathrm{CH}_2\mathrm{O}$$ and a molar mass of 180 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$

Question 11

Which of the following is the correct conversion factor to determine the number of molecules in 2.00 moles of $$\mathrm{H}_2\mathrm{O}$$?

Accepted Answer

$$2.00\ \mathrm{mol} 	imes 6.022 	imes 10$$^{23}$$\ \mathrm{molecules/mol}$$

Question 12

A sample contains 0.50 moles of $$\mathrm{O}_2. $$How many grams does this sample weigh? (Molar mass of $$\mathrm{O}_2 = 32.00\ \mathrm{g/mol})$$

Accepted Answer

$$16.00\ \mathrm{g}$$

Question 13

Which of the following best describes an aqueous solution?

Accepted Answer

A solution in which water is the solvent.

Question 14

A chemist has a 0.50 M solution of KNO$$_3. $$How many moles of KNO$$_3$$ are present in 250 mL of this solution?

Accepted Answer

$$0.125\ \mathrm{mol}$$

Question 15

Which of the following is NOT a correct step in determining the empirical formula from percent composition data?

Accepted Answer

Multiply all mole values by the molar mass of the compound.

Question 16

A solution is made by dissolving 10.0 g of NaCl (molar mass = 58.44 g/mol) in enough water to make 500 mL of solution. What is the molarity of the solution?

Accepted Answer

$$0.342\ M$$

Question 17

Which of the following best describes the process of dilution?

Accepted Answer

Adding more solvent to a solution to decrease its concentration.

Question 18

A compound contains 30.45% nitrogen and 69.55% oxygen by mass. What is the empirical formula of the compound? (Atomic masses: N = 14.01, O = 16.00)

Accepted Answer

$$\mathrm{NO}_2$$

Question 19

Which of the following is the correct calculation for the number of moles in 9.04 g of H$$_2O$$? (Molar mass = 18.016 g/mol)

Accepted Answer

$$\frac{9.04}{18.016} = 0.502\ \mathrm{mol}$$

Chemical Quantities, Empirical and Molecular Formulas, and Solution Concentration 09-08-26

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