Question 1

Which of the following compounds is classified as ionic, and why?

Accepted Answer

Potassium sulfide, because it contains a metal and a nonmetal.

Question 2

What is the correct name for the compound formed when $$\mathrm{Ca$$^{2+}$$}$$ and $$\mathrm{Br^-}$$ ions combine?

Accepted Answer

Calcium bromide

Question 3

What is the correct chemical formula for iron(III) carbonate?

Accepted Answer

$$\mathrm{Fe_2$(CO_3$)_3}$$

Question 4

Which of the following is the correct name for $$\mathrm{$$HNO_2$$} (aq$$)?

Accepted Answer

Nitrous acid

Question 5

A geologist analyzes a mineral and finds it contains $$3.50 	imes 10$$^{24}$$ atoms of aluminum. How many moles of aluminum is this? (Avogadro's number = 6.022$$ 	imes $$10^{23})$$

Accepted Answer

5.82 mol

Question 6

How many grams of calcium nitrate contain 2.10 moles of oxygen atoms? (Molar mass of calcium nitrate $$= 164.09 g/$$mol; $$\mathrm{Ca(NO_3$)_2}$$ contains 6 oxygen atoms per formula unit.)

Accepted Answer

68.4 g

Question 7

Maya earned $$615 by selling aluminum cans. The facility pays 0.75$ per mole of aluminum. How many pounds of aluminum did Maya recycle? (Molar mass of Al = 26.98$ g/mol; 453.59$ g = 1$ lb.)

Accepted Answer

23.7 lbs

Question 8

Which compound contains the greatest percent by mass of oxygen?

Accepted Answer

$$\mathrm{H_2O_2}$$

Question 9

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

Accepted Answer

CH$$_2O$$

Question 10

The empirical formula of a compound is $$\mathrm{C_3H_7N}$$ and the molar mass is $$201.3 g/$$mol. What is the molecular formula?

Accepted Answer

$$\mathrm{C_9H_{21}N_3$}$$

Question 11

What is the coefficient in front of $$\mathrm{O_2$} in $$the balanced equation below?

$$\mathrm{C_3H_8 + O_2$ \rightarrow CO_2$ + H_2O}$$

Accepted Answer

5

Question 12

When diphosphorus pentoxide reacts with water to produce phosphoric acid, what is the coefficient in front of water in the balanced equation?

Accepted Answer

2

Question 13

What type of reaction is represented by the reaction of diphosphorus pentoxide with water to produce phosphoric acid?

Accepted Answer

Combination / synthesis

Question 14

Predict the products and determine the correct balanced equation when $$\mathrm{Na_2CO_3}$$ and $$\mathrm{HCl}$$ are mixed.

Accepted Answer

$$\mathrm{Na_2CO_3 + 2 HCl \rightarrow 2 NaCl + CO_2$ + H_2O}$$

Question 15

Given the reaction $$2\ \mathrm{NO} + \mathrm{O_2$} \rightarrow 2\ \mathrm{NO_2$}$$, how many grams of nitrogen dioxide can be produced from 3.0 moles of $$\mathrm{O_2$}$$ and excess $$\mathrm{NO}$$? (Molar mass of $$\mathrm{NO_2$} = 46.01 g/$$mol.)

Accepted Answer

138 g

Question 16

A chemist reacts 56.0 g of nitrogen with 12.1 g of hydrogen according to the equation $$\mathrm{N_2$ + 3 H_2$ \rightarrow 2 NH_3$}. $$What is the theoretical yield, in moles, of ammonia? (Molar mass: $$\mathrm{N_2$} = 28.02 g/$$mol; $$\mathrm{H_2$} = 2.016 g/$$mol.)

Accepted Answer

1.99 mol

Question 17

Using the balanced equation $$2\ \mathrm{$$AlBr_3$$} + 3\ \mathrm{K_2SO_4} \rightarrow 6\ \mathrm{KBr} + \mathrm{Al_2$(SO_4$)_3}$$, what is the limiting reactant when 7.89 g of aluminum bromide reacts with 9.21 g of potassium sulfate?

Accepted Answer

Aluminum bromide ($$\mathrm{$$AlBr_3$$})$$

Question 18

A student reacts 0.850 mol of zinc with excess HCl and collects 0.640 mol of hydrogen gas according to $$\mathrm{Zn + 2 HCl \rightarrow $$ZnCl_2$$ + H_2$}. $$What is the percent yield of hydrogen?

Accepted Answer

75.3%

Question 19

Which of the following best describes why $$\mathrm{Fe_2$(CO_3$)_3} is $$the correct formula for iron(III) carbonate?

Accepted Answer

Because iron(III) has a $$+3$$ charge and carbonate has a $$-2$$ charge, so two iron ions balance three carbonate ions.

CHEM 139 Exam 2 Revision – Step-by-Step Study Guidance

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