Q: A 100 g sample of $$\text{CaCO}_3 ($$molar mass = 100 g/mol) is heated and produces 56 g of solid residue. Which balanced equation best describes the reaction?

$$\text{CaCO}_3(s) + \text{heat} \rightarrow \text{CaO}(s) + \text{CO}_2(g)$$

Q: Which of the following molecules would have the highest boiling point?

Ethanol ($$\text{CH}_3\text{CH}_2\text{OH})$$

Question 1

Which of the following statements best explains why the atomic radius increases as you move down a group in the periodic table?

Accepted Answer

Because additional electron shells are added, increasing the distance between the nucleus and the outermost electrons.

Question 2

A sample contains 0.5 moles of NaCl. How many formula units of NaCl are present in the sample? (Avogadro’s number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$3.011 	imes 10$$^{23}$$

Question 3

Which of the following electron configurations is isoelectronic with $$	ext{Ar}$$?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$

Question 4

Which of the following best describes the type of bonding and structure in sodium chloride (NaCl) crystal?

Accepted Answer

Ionic bonding with a crystal lattice

Question 5

A 100 g sample of $$	ext{CaCO}_3 ($$molar mass = 100 g/mol) is heated and produces 56 g of solid residue. Which balanced equation best describes the reaction?

Accepted Answer

$$	ext{CaCO}_3(s) + 	ext{heat} ightarrow 	ext{CaO}(s) + 	ext{CO}_2(g)$$

Question 6

Which of the following molecules would have the highest boiling point?

Accepted Answer

Ethanol ($$	ext{CH}_3	ext{CH}_2	ext{OH})$$

Question 7

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have loosely bound valence electrons that move freely in a 'sea of electrons'.

Question 8

A solution is made by dissolving 0.5 moles of NaCl in enough water to make 1.0 L of solution. What is the molarity of the solution?

Accepted Answer

0.5 M

Question 9

Which of the following changes will increase the rate of a chemical reaction according to collision theory?

Accepted Answer

Increasing the concentration of reactants

Question 10

Which of the following is the correct expression for the equilibrium constant ($$K_c) $$for the reaction: $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b}$$

Question 11

A reaction has $$\Delta H  0. $$Which of the following statements is true about the spontaneity of the reaction?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 12

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It decreases the activation energy, increasing the reaction rate.

Question 13

Which of the following aqueous solutions will act as a buffer with a pH \u003e 7? Assume all concentrations are 0.10 M.

Accepted Answer

CH$$_3NH$_2$$ and CH$$_3NH$_3Cl$$

Question 14

Which of the following best explains why increasing the temperature increases the rate of reaction?

Accepted Answer

More molecules have sufficient kinetic energy to overcome the activation energy barrier.

Question 15

Which of the following is the correct formula for calculating the energy required to heat a substance?

Accepted Answer

$$q = mc\Delta T$$

Question 16

Which of the following best describes the process occurring in a galvanic (voltaic) cell?

Accepted Answer

A spontaneous redox reaction generates electrical energy.

Question 17

Which of the following is the correct relationship between Gibbs free energy and the equilibrium constant?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 18

A buffer solution is prepared by mixing equal moles of acetic acid ($$	ext{CH}_3	ext{COOH}) $$and sodium acetate ($$	ext{CH}_3	ext{COONa}). $$What is the pH of the buffer if the $$pK_a of $$acetic acid is 4.76?

Accepted Answer

pH = 4.76

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