Question 1

Calculate the atomic mass of an element 'Y' that has two naturally occurring isotopes: Y-63 (mass = 62.9296 amu, abundance = 69.17%) and Y-65 (mass = 64.9278 amu, abundance = 30.83%). What is the atomic mass of Y?

Accepted Answer

$$63.55$$ amu

Question 2

How many moles are present in $$1.204 	imes 10$$^{24}$$ atoms of copper? (N_A = 6.022$$ 	imes $$10^{23}$$ atoms/mol)

Accepted Answer

$$2.00$$~moles

Question 3

How many grams of potassium are in $$0.750$$ moles of potassium? (Atomic mass of K = $$39.10 g/$$mol)

Accepted Answer

$$29.3$$~g

Question 4

What is the charge of chromium in the compound $$\mathrm{Cr_2O_3}$$?

Accepted Answer

$$+3$$

Question 5

What is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 6

What is the name for $$\mathrm{$$FeCl_3$$}$$?

Accepted Answer

iron (III) chloride

Question 7

The compound $$\mathrm{N_2O_5} is $$named:

Accepted Answer

dinitrogen pentoxide

Question 8

An aqueous solution of $$\mathrm{HBr} is $$named:

Accepted Answer

hydrobromic acid

Question 9

Give the name for $$\mathrm{H_2CO_3}.$$

Accepted Answer

carbonic acid

Question 10

What is the mass percent of hydrogen in $$\mathrm{C_2H_6O} ($$ethanol)? (Atomic masses: C = 12.01, H = 1.008, O = 16.00)

Accepted Answer

$$13.13\%$$

Question 11

Determine the empirical formula for a compound that is $$40.0\%$$ carbon, $$6.7\%$$ hydrogen, and $$53.3\%$$ oxygen by mass.

Accepted Answer

$$\mathrm{CH_2O}$$

Question 12

A compound has an empirical formula of $$\mathrm{CH_2$}$$ and a molar mass of $$56.0 g/$$mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C_4H_8}$$

Question 13

Write a balanced equation for the combustion of propane ($$\mathrm{C_3H_8}) in $$oxygen to form carbon dioxide and water.

Accepted Answer

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

Question 14

How many grams of sodium sulfate are needed to produce $$5.00 g of $$barium sulfate in the reaction: $$\mathrm{Na_2SO_4(aq) + $$BaCl_2$$(aq) \rightarrow 2 NaCl(aq) + $$BaSO_4$$(s)}$$? (Molar masses: Na$$_2SO$_4 = 142.04 g/$$mol, BaSO$$_4 = 233.39 g/$$mol)

Accepted Answer

$$3.04$$~g

Question 15

A sample contains $$0.500$$ moles of $$\mathrm{NH_4NO_3}. $$How many grams does this sample weigh? (Molar mass: $$\mathrm{NH_4NO_3} = 80.04 g/$$mol)

Accepted Answer

$$40.0$$~g

Question 16

Which of the following is the correct formula for hydrogen phosphate?

Accepted Answer

$$\mathrm{$$HPO_4$$^{2-}}$$

Question 17

If $$25.0 g of$$ $$\mathrm{N_2O_4}$$ reacts with excess $$\mathrm{N_2H_4}$$ according to $$\mathrm{N_2O_4(l) + 2 N_2H_4(l) \rightarrow 3 N_2$(g) + 4 H_2O(g)}$$, how many grams of $$\mathrm{N_2$}$$ are produced? (Molar masses: $$\mathrm{N_2O_4} = 92.02 g/$$mol, $$\mathrm{N_2$} = 28.02 g/$$mol)

Accepted Answer

$$22.9$$~g

Question 18

Which of the following ions is polyatomic and carries a $$-2$$ charge?

Accepted Answer

Sulfate ($$\mathrm{SO_4$^{2-}})$$

General Chemistry Exam 2 Study Guide: Atoms, Molecules, Compounds, and Chemical Reactions

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