Question 1

Which of the following statements best describes the concept of a mole in chemistry?

Accepted Answer

A mole is the amount of substance that contains as many entities as there are atoms in exactly 12 grams of carbon-12.

Question 2

What is the molar mass of glucose ($$C_6H_{12}O_6$)? (Atomic masses: C = 12.01, H = 1.01, O = 16.00)

Accepted Answer

$$180.16\ \mathrm{g/mol}$$

Question 3

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. What is the mass of this sample? (Molar mass of CO_2$ = 44.01$$\ \mathrm{g/mol}$$)

Accepted Answer

$$11.0\ \mathrm{g}$$

Question 4

Which of the following best explains why water ($$H_2O) is a $$polar molecule?

Accepted Answer

Water has a bent molecular geometry and the dipole moments do not cancel out.

Question 5

How many moles of $$NaCl$$ are present in $$117\ \mathrm{g} of$$ $$NaCl$$? (Molar mass of $$NaCl$$ = $$58.44\ \mathrm{g/mol})$$

Accepted Answer

$$2.00\ \mathrm{mol}$$

Question 6

Which of the following is the correct Lewis structure for ammonia ($$NH_3$$)?

Accepted Answer

A nitrogen atom with three single bonds to hydrogen atoms and one lone pair on nitrogen.

Question 7

Balance the following chemical equation: $$C_2H_6 + O_2$ \rightarrow CO_2$ + H_2O$$

Accepted Answer

$$2C_2H_6 + 7O_2 \rightarrow 4CO_2 + 6H_2O$$

Question 8

A reaction is carried out with $$10.0\ \mathrm{g} of$$ $$H_2$$ and excess $$O_2 to $$produce water. What mass of water ($$H_2O) $$can be formed? (Molar mass: $$H_2 = 2.02$$\ \mathrm{g/mol}$$, H_2O = 18.02$$\ \mathrm{g/mol}$$)

Accepted Answer

Question 9

Which of the following molecules is nonpolar?

Accepted Answer

$$CO_2$$

Question 10

How many oxygen atoms are present in $$3.00\ \mathrm{mol} of$$ $$H_2SO_4$$?

Accepted Answer

$$7.23 	imes 10$$^{24}$$

Question 11

Which of the following best describes the VSEPR model for predicting molecular geometry?

Accepted Answer

Electron groups (bonding pairs or lone pairs) stay as far apart as possible in 3D space to minimize electron-electron repulsion.

Question 12

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$$CH_2O$$

Question 13

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4$$)?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 14

If $$2.00\ \mathrm{mol} of$$ $$Al$$ reacts with $$3.00\ \mathrm{mol} of$$ $$Cl_2 to $$form $$AlCl_3$$, what is the limiting reactant?

Accepted Answer

$$Cl_2$$

Question 15

Which of the following statements about molar mass is correct?

Accepted Answer

The molar mass of a compound is the mass in grams of one mole of that compound.

Question 16

Which of the following best describes a chemical equation that is balanced?

Accepted Answer

The number of atoms of each element is the same on both sides of the equation.

Question 17

A sample of $$CaCO_3$$ has a mass of $$50.0\ \mathrm{g}. $$How many moles of $$CaCO_3$$ are present? (Molar mass = $$100.09\ \mathrm{g/mol})$$

Accepted Answer

$$0.500\ \mathrm{mol}$$

Question 18

Which of the following is a correct statement about the relationship between atomic mass units (u) and grams?

Accepted Answer

1 mole of a substance has a mass in grams equal to its atomic or molecular mass in atomic mass units (u).

Question 19

Which of the following best describes the process of determining the empirical formula of a compound?

Accepted Answer

Convert the mass percentages to moles, divide by the smallest number of moles, and round to the nearest whole number.

Moles, Molar Masses, and Chemical Equations: General Chemistry Study Notes

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