Question 1

Consider the balanced chemical equation for the combustion of ethanol ($$\mathrm{C_2H_5OH}) to $$all coefficients as the simplest whole number. What is the sum of all of the coefficients in the balanced equation?

Accepted Answer

$$9$$

Question 2

Which of the following represents the decomposition of a molecular compound?

Accepted Answer

$$2\ \mathrm{Al_2O_3} \rightarrow 4\ \mathrm{Al} + 3\ \mathrm{O_2$}$$

Question 3

How many gold atoms are present in a small gold flake that weighs $$0.002582\ \mathrm{g}$$? (Molar mass of Au = $$196.97\ \mathrm{g/mol})$$

Accepted Answer

$$7.89 	imes 10$$^{18}$$

Question 4

How much would $$0.729$$ mol of caffeine weigh in grams? (Molar mass of caffeine = $$194.19\ \mathrm{g/mol})$$

Accepted Answer

$$141.6\ \mathrm{g}$$

Question 5

An $$8.4\ \mathrm{g}$$ sample of caffeine contains how many caffeine molecules? (Molar mass of caffeine = $$194.19\ \mathrm{g/mol}$$, Avogadro's number $$= 6.022 	imes 10$$^{23}$$)

Accepted Answer

$$2.61 	imes 10$$^{22}$$

Question 6

A $$25.4\ \mathrm{g}$$ sample of caffeine contains how many nitrogen atoms? (Caffeine formula: $$\mathrm{C_8H_{10}N_4O_2}$$, Molar mass = $$194.19\ \mathrm{g/mol}$$, Avogadro's number $$= 6.022 	imes 10$$^{23}$$)

Accepted Answer

$$3.15 	imes 10$$^{23}$$

Question 7

A sample of caffeine contains $$8.54 	imes 10$$^{24}$$ carbon atoms. How much does this sample weigh in grams? (Caffeine formula: $$\mathrm{C_8H_{10}N_4O_2}$$, Molar mass = 194.19$$\ \mathrm{g/mol}$$)

Accepted Answer

$$275\ \mathrm{g}$$

Question 8

A decomposition experiment determined that glucose possesses an empirical formula of $$\mathrm{CH_2O}. A $$mass spectrometry experiment determined that glucose has a molecular weight of approximately $$180\ \mathrm{amu}. $$What is the molecular formula of glucose?

Accepted Answer

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

Question 9

How many grams of $$\mathrm{H_2$}$$ could be produced by the complete reaction of $$0.327$$ mol of $$\mathrm{H_3PO_4}$$? (Reaction: $$2\ \mathrm{Fe} + 2\ \mathrm{H_3PO_4} \rightarrow 2\ \mathrm{$$FePO_4$$} + 3\ \mathrm{H_2$}$$, Molar mass $$\mathrm{H_2$} = 2.016\ \mathrm{g/mol})$$

Accepted Answer

$$0.987\ \mathrm{g}$$

Question 10

If $$94.51$$ grams of iron reacts, how much phosphoric acid, in grams, is required? (Reaction: $$2\ \mathrm{Fe} + 2\ \mathrm{H_3PO_4} \rightarrow 2\ \mathrm{$$FePO_4$$} + 3\ \mathrm{H_2$}$$, Molar masses: Fe = $$55.85\ \mathrm{g/mol}$$, $$\mathrm{H_3PO_4}$$ = $$97.99\ \mathrm{g/mol})$$

Accepted Answer

$$166\ \mathrm{g}$$

Question 11

If $$7.25 	imes 10$$^{22}$$ molecules of $$\mathrm{$$H_2$$}$$ are produced, how many grams of iron reacted? (Reaction: 2$$\ \mathrm{Fe} + 2\ \mathrm{H_3PO_4} ightarrow 2\ \mathrm{$$FePO_4$$} + 3\ \mathrm{$$H_2$$}$$, Molar mass Fe = 55.85$$\ \mathrm{g/mol}$$)

Accepted Answer

$$44.9\ \mathrm{g}$$

Question 12

When $$25.0\ \mathrm{g} of Mg $$reacts with $$55.0\ \mathrm{g} of$$ $$\mathrm{$$AlCl_3$$}$$, how much Al solid is produced, in grams? (Reaction: $$3\ \mathrm{Mg} + 2\ \mathrm{$$AlCl_3$$} \rightarrow 2\ \mathrm{Al} + 3\ \mathrm{$$MgCl_2$$}$$, Molar masses: Mg = $$24.31\ \mathrm{g/mol}$$, Al = $$26.98\ \mathrm{g/mol}$$, $$\mathrm{$$AlCl_3$$}$$ = $$133.34\ \mathrm{g/mol})$$

Accepted Answer

$$9.08\ \mathrm{g}$$

Question 13

A reaction is conducted with $$76\%$$ yield and $$8.95\ \mathrm{g} of $$aluminum metal is collected. How much magnesium, in grams, must have reacted? (Reaction: $$3\ \mathrm{Mg} + 2\ \mathrm{$$AlCl_3$$} \rightarrow 2\ \mathrm{Al} + 3\ \mathrm{$$MgCl_2$$}$$, Molar mass Mg = $$24.31\ \mathrm{g/mol}$$, Al = $$26.98\ \mathrm{g/mol})$$

Accepted Answer

$$12.8\ \mathrm{g}$$

Question 14

Which of the following diagrams best represents an aqueous solution of ethanol, $$\mathrm{CH_3CH_2OH}$$?

Accepted Answer

Diagram A (shows molecules evenly dispersed, no ions)

Question 15

What is the net ionic equation for the reaction that occurs between $$\mathrm{Hg_2$(NO_3$)_2} (aq) $$and $$\mathrm{Sr(OH)_2} (aq$$)?

Accepted Answer

$$\mathrm{Hg_2$^{2+} (aq) + 2OH^- (aq) \rightarrow Hg_2$(OH)_2 (s)}$$

Question 16

What is the oxidation number of carbon in $$\mathrm{Na_2CO_3}$$?

Accepted Answer

$$+4$$

Question 17

A $$15.0\ \mathrm{mL} of$$ $$2.50\ \mathrm{M}$$ $$\mathrm{Ca(NO_3$)_2}$$ solution is transferred to a $$500\ \mathrm{mL}$$ volumetric flask and diluted to the mark. What is the concentration of nitrate ion in the flask in molarity?

Accepted Answer

$$0.15\ \mathrm{M}$$

Question 18

Titration of a $$20.00\ \mathrm{mL}$$ sample of phosphoric acid required $$18.75\ \mathrm{mL} of$$ $$0.8411\ \mathrm{M}$$ NaOH to reach the end point. If phosphoric acid is a triprotic acid, what is the concentration of phosphoric acid in this sample in molarity?

Accepted Answer

$$0.263\ \mathrm{M}$$

Question 19

Consider the neutralization of solid $$\mathrm{Ca(OH)_2} by a $$HCl solution. How many mL of $$0.1500\ \mathrm{M}$$ HCl are required to completely neutralize $$5.00\ \mathrm{g} of$$ $$\mathrm{Ca(OH)_2}$$? (Molar masses: $$\mathrm{Ca(OH)_2} = 74.09\ \mathrm{g/mol}$$, $$\mathrm{HCl} = 36.46\ \mathrm{g/mol})$$

Accepted Answer

$$900\ \mathrm{mL}$$

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