Q: A sample contains $$4.5 \times 10$$^{24}$$ molecules of CO_2$. How many moles of CO_2$ are present?

$$7.48 \times 10$$^{-1}$$ moles

Question 1

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound has a fixed composition with elements chemically bonded, while a mixture consists of substances physically combined in variable proportions.

Question 2

Which of the following electron configurations represents a noble gas?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 3

How many moles are present in 7.50 g of lithium metal ($$Li$$, molar mass = 6.94 g/mol)?

Accepted Answer

$$1.08$$ moles

Question 4

A sample contains $$4.5 	imes 10$$^{24}$$ molecules of CO_2$. How many moles of CO_2$ are present?

Accepted Answer

$$7.48 	imes 10$$^{-1}$$ moles

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 6

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

Accepted Answer

Water has a bent shape and an unequal distribution of electrons due to differences in electronegativity.

Question 7

A reaction releases $$150 kJ of $$heat. Which term best describes this reaction?

Accepted Answer

Exothermic

Question 8

What is the molarity of a solution made by dissolving $$14.8 g of$$ $$KBr ($$molar mass = $$119 g/$$mol) in enough water to make $$250 mL of $$solution?

Accepted Answer

$$0.497 M$$

Question 9

Which of the following best describes the difference between ionic and covalent bonding?

Accepted Answer

Ionic bonding involves the transfer of electrons from one atom to another, while covalent bonding involves the sharing of electrons.

Question 10

A gas sample at $$25^\circ C$$ occupies $$1.20 L at$$ $$0.980$$ atm. What volume will it occupy at $$45^\circ C ($$pressure constant)?

Accepted Answer

$$1.28 L$$

Question 11

Which of the following is oxidized in the reaction: $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$?

Accepted Answer

$$CO$$

Question 12

Which of the following statements about catalysts is correct?

Accepted Answer

A catalyst increases the rate of a reaction by providing an alternative pathway with lower activation energy.

Question 13

Which of the following is the correct net ionic equation for the reaction between $$AgNO_3$$ and $$NaCl in $$aqueous solution?

Accepted Answer

$$Ag^+ (aq) + Cl^- (aq) \rightarrow AgCl (s)$$

Question 14

A sealed container has a gas pressure of $$0.835$$ atm. Atmospheric pressure is $$760$$ mmHg. What is the pressure in mmHg inside the container?

Accepted Answer

$$634$$ mmHg

Question 15

Which of the following best describes what happens to the rate of a chemical reaction if the temperature increases?

Accepted Answer

The rate increases because more molecules have enough energy to overcome the activation energy barrier.

Question 16

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 17

A photon has a wavelength of $$525 nm. $$Calculate its energy. ($$h = 6.626 	imes 10$$^{-34}$$ J·s, c = 3.00$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$3.79 	imes 10$$^{-19}$$ J

Question 18

Which of the following best describes what is reduced in the reaction: $$Zn + Cu$$^{2+}$$ \rightarrow Zn$$^{2+}$$ + Cu$$?

Accepted Answer

$$Cu^{2+}$$

Question 19

Which of the following is a correct statement about the solubility of $$NaCl in $$water?

Accepted Answer

$$NaCl$$ dissolves in water because the polar water molecules stabilize the ions.

Question 20

Which of the following best describes the effect of increasing the concentration of reactants on the rate of a chemical reaction?

Accepted Answer

The rate increases because there are more frequent effective collisions.

General Chemistry I Final Exam Review: Key Concepts and Practice Problems

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