Q: Which of the following is the correct calculation for the molar mass of the empirical formula C2H3O?

$$2 \times 12.011 + 3 \times 1.008 + 16.00 = 43.046 g/$$mol

Question 1

A compound is found to contain 40.1% C, 6.6% H, and 53.3% O by mass. What is the empirical formula of this compound?

Accepted Answer

CH2O

Question 2

A compound containing only C and H produces 1.60 g CO2 and 0.819 g H2O upon combustion. If the original sample mass was 0.8233 g, what is the empirical formula of the compound?

Accepted Answer

C10H12O

Question 3

Given the empirical formula C2H3O and a molar mass of 86.09 g/mol, what is the molecular formula of the compound?

Accepted Answer

C4H6O2

Question 4

A compound has the empirical formula CH and a molar mass of 78.11 g/mol. What is its molecular formula?

Accepted Answer

C6H6

Question 5

Which of the following best describes the process of combustion analysis for determining empirical formulas?

Accepted Answer

Burning a compound in pure oxygen and measuring the masses of CO2 and H2O produced.

Question 6

When balancing the equation $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$, what is the correct set of coefficients?

Accepted Answer

$$1, 2, 1, 2$$

Question 7

If you start with 1.234 g of methane ($$\mathrm{CH_4$}$$), how many grams of oxygen ($$\mathrm{O_2$}) $$are required for complete combustion?

Accepted Answer

4.9228 g

Question 8

Which equation represents the balanced decomposition of potassium chlorate ($$\mathrm{$$KClO_3$$}) $$when heated?

Accepted Answer

$$\mathrm{2KClO_3(s) \rightarrow 2KCl(s) + 3O_2(g)}$$

Question 9

A student is asked to balance the equation $$\mathrm{C_4H_{10}(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}. $$Which of the following is the correct set of coefficients?

Accepted Answer

$$2, 13, 8, 10$$

Question 10

Which of the following statements about empirical and molecular formulas is TRUE?

Accepted Answer

The molecular formula is always a whole-number multiple of the empirical formula.

Question 11

A solution is prepared by diluting 50.0 mL of 2.00 M NaCl to a final volume of 200.0 mL. What is the final concentration?

Accepted Answer

0.25 M

Question 12

Which of the following is NOT a unit commonly used for solution concentration?

Accepted Answer

Pressure percentage

Question 13

In combustion analysis, why can't the amount of oxygen in a compound be determined directly?

Accepted Answer

Oxygen is determined by difference, not by direct measurement.

Question 14

Which of the following best describes a balanced chemical equation?

Accepted Answer

The number of atoms of each element is equal on both sides of the equation.

Question 15

If 0.076918 mol of methane ($$\mathrm{CH_4$}) is $$combusted, how many moles of water ($$\mathrm{H_2O}) $$are produced?

Accepted Answer

0.153836 mol

Question 16

Which of the following is the correct balanced equation for the reaction between solid silicon dioxide and solid carbon to produce solid silicon carbide and carbon monoxide gas?

Accepted Answer

$$\mathrm{$$SiO_2$$(s) + C(s) \rightarrow SiC(s) + CO(g)}$$

Question 17

A chemical equation is written as $$\mathrm{A + B \rightarrow C + D}. $$Which of the following statements is correct?

Accepted Answer

A and B are reactants; C and D are products.

Question 18

Which of the following is a correct interpretation of the balanced equation $$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(g)}$$?

Accepted Answer

One mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and two moles of water.

Question 19

Which of the following is the correct calculation for the molar mass of the empirical formula C2H3O?

Accepted Answer

$$2 	imes 12.011 + 3 	imes 1.008 + 16.00 = 43.046 g/$$mol

chapter 3 lec 2

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