Q: How many particles are in one mole of any substance, and what is this number called?

$$6.02 \times 10$$^{23}$$ particles, known as Avogadro's number.

Q: How many grams of glucose ($$\mathrm{C_6H_{12}O_6$}$$, molar mass $$= 180\ \mathrm{g/mol}) $$are in $$3.55$$ moles?

$$640\ \mathrm{g}$$,\quad$$ using 3.55$$ \times 180$

Question 1

Which of the following best explains why sodium forms a $$\mathrm{Na^+}$$ ion when reacting with chlorine in table salt?

Accepted Answer

Sodium loses one electron to achieve a noble gas configuration.

Question 2

When iodine forms an ion, what is the resulting charge and why?

Accepted Answer

Iodine gains one electron to form $$\mathrm{I^-}$$, achieving a full octet.

Question 3

What is the correct chemical formula for iron(III) sulfide, and what does the (III) indicate?

Accepted Answer

$$\mathrm{Fe_2S_3}$$; the (III) indicates iron has a $$+3$$ charge.

Question 4

Which of the following best describes a polyatomic ion?

Accepted Answer

A group of covalently bonded atoms with an overall charge.

Question 5

Which compound contains an ionic bond and why?

Accepted Answer

$$\mathrm{CaO}$$, because it is formed from a metal and a nonmetal.

Question 6

What is the molecular geometry of water ($$\mathrm{H_2O}$$), and what causes this shape?

Accepted Answer

Bent (109°), due to two lone pairs on oxygen.

Question 7

Which type of intermolecular force is primarily responsible for the high boiling point of ammonia ($$\mathrm{NH_3$}$$)?

Accepted Answer

Hydrogen bonding

Question 8

How many particles are in one mole of any substance, and what is this number called?

Accepted Answer

$$6.02 	imes 10$$^{23}$$ particles, known as Avogadro's number.

Question 9

How many moles of carbon atoms are present in $$0.500$$ mole of $$\mathrm{C_2H_6}$$?

Accepted Answer

$$1.00$$ mole, because each molecule contains two carbon atoms.

Question 10

A patient receives $$75.0 g of $$water intravenously. How many moles of water is this?

Accepted Answer

$$4.16$$ moles$$,\quad$$ using $$\mathrm{moles = \frac{mass}{molar\ mass}}$$ with $$18.0\ \mathrm{g/mol}.$$

Question 11

How many grams of glucose ($$\mathrm{C_6H_{12}O_6$}$$, molar mass $$= 180\ \mathrm{g/mol}) $$are in $$3.55$$ moles?

Accepted Answer

$$640\ \mathrm{g}$$,\quad$$ using 3.55$$ 	imes 180$

Question 12

Given the reaction $$2\mathrm{Al} + 6\mathrm{HCl} \rightarrow 3\mathrm{H_2$} + 2\mathrm{$$AlCl_3$$}$$, how many moles of HCl are required to react with $$0.345$$ mole of Al?

Accepted Answer

$$1.04$$ moles$$,\quad$$ using $$0.345 	imes \frac{6}{2}$$

Question 13

In the reaction $$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$, how many grams of $$\mathrm{CO_2$}$$ are produced from $$125 g of$$ $$\mathrm{O_2$}$$ and excess $$\mathrm{CH_4$}$$?

Accepted Answer

$$85.9\ \mathrm{g}$$,\quad$ using stoichiometry and molar masses.

Question 14

A gas sample at $$5.00$$ atm and $$5.0\ ^\circ\mathrm{C} is $$heated to $$40.0\ ^\circ\mathrm{C} at $$constant volume. What is the new pressure?

Accepted Answer

$$5.63$$ atm$$,\quad$$ using $$\frac{P_1$}{T_1$} = \frac{P_2$}{T_2$}$$ with temperatures in Kelvin.

Question 15

A sample of nitrogen gas has a volume of $$500 mL at$$ $$740$$ torr and $$25\ ^\circ\mathrm{C}. $$What is the new volume at $$760$$ torr and $$50\ ^\circ\mathrm{C} ($$amount of gas constant)?

Accepted Answer

$$530 mL$,\quad$$ using the combined gas law.

Question 16

A gas sample contains $$4.0 g of$$ $$\mathrm{CH_4$}$$ and $$2.0 g of He. $$What is the total volume at STP?

Accepted Answer

$$17 L$,\quad$$ using $$\mathrm{V = nRT/P}$$ and total moles.

Question 17

If $$8.0 g of$$ $$\mathrm{O_2$} ($$molar mass $$= 32\ \mathrm{g/mol}) $$occupies $$2.6 L$$, what will the volume be if $$10 g of Ne ($$molar mass $$= 20\ \mathrm{g/mol}) is $$added at constant $$T$$ and $$P$$?

Accepted Answer

$$7.8 L$,\quad$$ using $$\frac{n_1$ + n_2$}{n_1$} 	imes V_1$

Question 18

Which of the following changes will increase the pressure of a gas in a closed container, assuming volume and amount of gas are constant?

Accepted Answer

Increasing the temperature of the gas.

Question 19

A scuba diver ascends rapidly from deep water to the surface. Which gas law explains why the volume of air in the diver's lungs increases as pressure decreases?

Accepted Answer

Boyle's Law: $$P_1V_1 = P_2V_2$$

GOB Chemistry Exam Study Guidance

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