Question 1

A compound is found to contain 40.00% carbon, 6.71% hydrogen, and 53.29% oxygen by mass. What is the empirical formula of this compound?

Accepted Answer

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

Question 2

A 1.25 g sample of a compound containing only carbon, hydrogen, and oxygen is combusted, producing 2.75 g of $$\mathrm{CO}_2$$ and 1.13 g of $$\mathrm{H}_2\mathrm{O}. $$What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{C}_3\mathrm{H}_8\mathrm{O}$$

Question 3

A sample of a platinum compound used in chemotherapy contains 65.02% Pt, 9.34% N, 2.02% H, and 23.62% Cl by mass. What is the empirical formula of this compound?

Accepted Answer

$$\mathrm{PtCl}_2\mathrm{(NH}_3)_2$$

Question 4

Which of the following statements about the balanced reaction $$2\mathrm{Al}(s) + 6\mathrm{HCl}(aq) \rightarrow 2\mathrm{AlCl}_3(aq) + 3\mathrm{H}_2(g) is $$correct?

Accepted Answer

2 moles of aluminum react with 6 moles of hydrochloric acid to produce 3 moles of hydrogen gas.

Question 5

A 0.456 g mixture of sodium chloride and sodium nitrate is analyzed. After dissolving in water and precipitating with silver nitrate, 0.107 g of silver chloride is recovered. What is the mass percent of sodium chloride in the original mixture? ($$\mathrm{AgCl}$$ molar mass = $$143.32\ \mathrm{g/mol}$$, $$\mathrm{NaCl}$$ molar mass = $$58.44\ \mathrm{g/mol})$$

Accepted Answer

17.2%

Question 6

When balancing the combustion of ethanol, $$\mathrm{C}_2\mathrm{H}_5\mathrm{OH}(l) + O_2$(g) \rightarrow CO_2$(g) + H_2O(l)$$, what is the coefficient in front of $$O_2 in $$the balanced equation?

Accepted Answer

3

Question 7

A 10.0 g sample of magnesium reacts with 60.0 g of iodine to form magnesium iodide. What is the percent yield if 50.0 g of magnesium iodide is actually collected? (Molar mass $$\mathrm{MgI}_2 = 278.11\ \mathrm{g/mol})$$

Accepted Answer

77.7%

Question 8

If 29.0 g of butane ($$\mathrm{C}_4\mathrm{H}_{10}) is $$combusted completely, how many grams of $$O_2$$ are required? (Molar mass $$\mathrm{C}_4\mathrm{H}_{10} = 58.12\ \mathrm{g/mol}$$, $$O_2 = 32.00$$\ \mathrm{g/mol}$$, balanced equation: 2$$\mathrm{C}_4\mathrm{H}_{10} + 13\mathrm{O}_2 \rightarrow 8\mathrm{CO}_2 + 10\mathrm{H}_2O$$)

Accepted Answer

93.2 g

Question 9

A chemist decomposes 50.0 g of magnesium carbonate ($$\mathrm{MgCO}_3) by $$heating, and collects 20.0 g of magnesium oxide ($$\mathrm{MgO}). $$What is the percent yield? (Molar mass $$\mathrm{MgCO}_3 = 84.31\ \mathrm{g/mol}$$, $$\mathrm{MgO} = 40.30\ \mathrm{g/mol}$$, $$\mathrm{MgCO}_3 \rightarrow \mathrm{MgO} + \mathrm{CO}_2)$$

Accepted Answer

57.6%

Question 10

In the reaction $$2\mathrm{NH}_3(g) + 3\mathrm{CuO}(s) \rightarrow N_2$(g) + 3\mathrm{Cu}(s) + 3\mathrm{H}_2O(g)$$, if 34.0 g of $$\mathrm{NH}_3$$ and 40.0 g of $$\mathrm{CuO}$$ are reacted, what is the limiting reactant? (Molar masses: $$\mathrm{NH}_3 = 17.03\ \mathrm{g/mol}$$, $$\mathrm{CuO} = 79.55\ \mathrm{g/mol})$$

Accepted Answer

$$\mathrm{CuO}$$

Question 11

A 0.255 g sample of an alcohol (containing only C, H, and O) produces 0.561 g of $$\mathrm{CO}_2$$ and 0.306 g of $$\mathrm{H}_2O$$ upon combustion. What is the empirical formula of the alcohol?

Accepted Answer

$$\mathrm{C}_2\mathrm{H}_6\mathrm{O}$$

Question 12

Which of the following best describes the limiting reactant in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, thus limiting the amount of product formed.

Question 13

A reaction has a theoretical yield of 5.00 g of product, but only 3.75 g is actually collected. What is the percent yield?

Accepted Answer

80.0%

Question 14

If 150.0 g of aluminum reacts with 150.0 g of potassium according to $$\mathrm{AlI}_3 + 3\mathrm{K} \rightarrow 3\mathrm{KI} + \mathrm{Al}$$, how many grams of aluminum are produced? (Molar masses: $$\mathrm{AlI}_3 = 407.68\ \mathrm{g/mol}$$, $$\mathrm{K} = 39.10\ \mathrm{g/mol}$$, $$\mathrm{Al} = 26.98\ \mathrm{g/mol})$$

Accepted Answer

6.64 g

Question 15

A 1.00 g sample of a compound containing only C, H, and O is combusted, producing 1.47 g of $$\mathrm{CO}_2$$ and 0.60 g of $$\mathrm{H}_2O. If $$the molar mass of the compound is 60.0 g/mol, what is its molecular formula?

Accepted Answer

$$\mathrm{C}_3\mathrm{H}_6\mathrm{O}_2$$

Question 16

Which of the following is the correct balanced equation for the decomposition of potassium chlorate to form potassium chloride and oxygen gas?

Accepted Answer

$$2\mathrm{KClO}_3(s) \rightarrow 2\mathrm{KCl}(s) + 3\mathrm{O}_2(g)$$

Question 17

A reaction mixture contains 8 slices of bread, 5 pieces of chicken, and 3 pieces of cheese. If a sandwich requires 2 slices of bread, 1 piece of chicken, and 1 piece of cheese, what is the limiting reactant and how many sandwiches can be made?

Accepted Answer

Cheese; 3 sandwiches

Question 18

In gravimetric analysis, which of the following best describes the process?

Accepted Answer

Using the mass of a precipitate to determine the amount of a specific ion in a sample.

Mass Relationships in Chemical Reactions: General Chemistry Study Notes

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