Q: How many grams of NaCl (molar mass = 58.44 g/mol) are required to prepare 0.250 mol of NaCl solution?

$$0.250 \times 58.44 = 14.61 g$$

Q: A reaction has a theoretical yield of 25.0 g, but only 18.0 g of product is actually obtained. What is the percent yield?

$$\frac{18.0}{25.0} \times 100 = 72\%$$

Q: A solution is prepared by dissolving 5.00 g of CaCl$$_2 ($$molar mass = 110.98 g/mol) in water. How many moles of Cl$$^-$$ ions are present in the solution?

$$\frac{5.00}{110.98} \times 2 = 0.0901$$ mol

Question 1

A 0.500 g sample of an unknown hydrocarbon is combusted in excess oxygen, producing 1.54 g of CO$$_2$$ and 0.630 g of H$$_2O. $$What is the empirical formula of the hydrocarbon?

Accepted Answer

C$$_3H$_8$$

Question 2

Which of the following best describes a strong electrolyte in aqueous solution?

Accepted Answer

A substance that completely dissociates into ions in water.

Question 3

How many grams of NaCl (molar mass = 58.44 g/mol) are required to prepare 0.250 mol of NaCl solution?

Accepted Answer

$$0.250 	imes 58.44 = 14.61 g$$

Question 4

Which of the following is the correct balanced equation for the combustion of propane (C$$_3H$_8$$)?

Accepted Answer

$$\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$$

Question 5

If 10.0 g of H$$_2$$ reacts with 80.0 g of O$$_2 to $$form water, what is the limiting reagent?

Accepted Answer

H$$_2$$

Question 6

A reaction has a theoretical yield of 25.0 g, but only 18.0 g of product is actually obtained. What is the percent yield?

Accepted Answer

$$\frac{18.0}{25.0} 	imes 100 = 72\%$$

Question 7

Which of the following compounds is a strong acid?

Accepted Answer

HCl

Question 8

Which of the following is the net ionic equation for the reaction between aqueous solutions of Na$$_2SO$_4$$ and BaCl$$_2$$?

Accepted Answer

$$\mathrm{Ba$$^{2+}$$ (aq) + SO_4$^{2-} (aq) \rightarrow $$BaSO_4$$ (s)}$$

Question 9

Which of the following statements about oxidation and reduction is correct?

Accepted Answer

Oxidation is the loss of electrons; reduction is the gain of electrons.

Question 10

Assign the oxidation number to sulfur in H$$_2SO$_4.$$

Accepted Answer

+6

Question 11

Which of the following substances will NOT dissociate into ions when dissolved in water?

Accepted Answer

C$$_6H$_{12}O$_6$$

Question 12

A solution is prepared by dissolving 5.00 g of CaCl$$_2 ($$molar mass = 110.98 g/mol) in water. How many moles of Cl$$^-$$ ions are present in the solution?

Accepted Answer

$$\frac{5.00}{110.98} 	imes 2 = 0.0901$$ mol

Question 13

Which of the following is a correct molecular equation for the reaction between aqueous solutions of AgNO$$_3$$ and NaCl?

Accepted Answer

$$\mathrm{$$AgNO_3$$ (aq) + NaCl (aq) \rightarrow AgCl (s) + $$NaNO_3$$ (aq)}$$

Question 14

Which of the following is a weak base?

Accepted Answer

NH$$_3$$

Question 15

If 2.00 mol of Al reacts with 3.00 mol of Cl$$_2 to $$form AlCl$$_3$$, what is the limiting reagent?

Accepted Answer

Cl$$_2$$

Question 16

Which of the following best describes a nonelectrolyte?

Accepted Answer

A substance that does not conduct electricity when dissolved in water.

Question 17

Which of the following reactions will result in the formation of a precipitate?

Accepted Answer

Mixing solutions of Pb(NO$$_3$$)$$_2$$ and KI

Question 18

In the reaction $$\mathrm{2Fe_2O_3 + 3C \rightarrow 4Fe + 3CO_2}$$, how many moles of Fe are produced from 2.0 mol of Fe$$_2O$_3$$?

Accepted Answer

$$2.0 	imes \frac{4}{2} = 4.0$$ mol

Question 19

Which of the following is the total ionic equation for the reaction between HCl(aq) and NaOH(aq)?

Accepted Answer

$$\mathrm{H^+ (aq) + Cl^- (aq) + Na^+ (aq) + OH^- (aq) \rightarrow Na^+ (aq) + Cl^- (aq) + H_2O (l)}$$

Chapter 7: Chemical Reactions and Stoichiometry – Study Notes

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