Q: In the Determination of Equilibrium Constant experiment, the equilibrium constant $$K_{eq}$$ for the reaction $$A + B \rightleftharpoons C is $$calculated using the concentrations at equilibrium. If $$[A] = 0.2\,M$$, $$[B] = 0.3\,M$$, and $$[C] = 0.4\,M$$, what is $$K_{eq}$$?

$$K_{eq} = \frac{[C]}{[A][B]} = \frac{0.4}{0.2 \times 0.3} = 6.67$$

Q: In the Determination of Solubility Product of $$Ca(OH)_2$$ experiment, the solubility product constant ($$K_{sp}) is $$calculated using the concentrations of $$Ca^{2+}$$ and $$OH^-$$ ions. If $$[Ca$$^{2+}$$] = 0.01\,M$$ and $$[OH^-] = 0.02\,M$$, what is $$K_{sp}$$?

$$K_{sp} = [Ca$$^{2+}$$] \times [OH^-]^2 = 0.01 \times (0.02)^2$ = 0.000004$$

Q: A calorimetry experiment measures the temperature change when 50.0 g of water absorbs 420 J of heat. What is the temperature change ($$\Delta T) of $$the water? (Specific heat of water $$c = 4.18\,J/g\cdot K)$$

$$\Delta T = \frac{420}{50 \times 4.18} = 2.01\,K$$

Question 1

In the Rate of Chemical Reactions experiment, a student measures the time it takes for a reaction to complete at two different temperatures. Which of the following best explains why the reaction rate increases with temperature?

Accepted Answer

Higher temperature increases the kinetic energy of molecules, resulting in more frequent and energetic collisions.

Question 2

A reaction is performed in a closed system and reaches equilibrium. According to Le Chatelier’s Principle, what will happen if the concentration of a reactant is increased?

Accepted Answer

The equilibrium will shift to produce more products.

Question 3

In the Determination of Equilibrium Constant experiment, the equilibrium constant $$K_{eq}$$ for the reaction $$A + B \rightleftharpoons C is $$calculated using the concentrations at equilibrium. If $$[A] = 0.2\,M$$, $$[B] = 0.3\,M$$, and $$[C] = 0.4\,M$$, what is $$K_{eq}$$?

Accepted Answer

$$K_{eq} = \frac{[C]}{[A][B]} = \frac{0.4}{0.2 	imes 0.3} = 6.67$$

Question 4

A buffer solution is prepared by mixing acetic acid ($$CH_3COOH) $$and sodium acetate ($$CH_3COONa). $$Which equation best describes the pH of this buffer?

Accepted Answer

$$pH = pK_a + \log \left( \frac{[CH_3COONa]}{[CH_3COOH]} \right)$$

Question 5

During an acid-base titration, a student titrates 25.0 mL of $$0.100\,M$$ HCl with $$0.100\,M$$ NaOH. What is the volume of NaOH required to reach the equivalence point?

Accepted Answer

25.0 mL

Question 6

In the Determination of Solubility Product of $$Ca(OH)_2$$ experiment, the solubility product constant ($$K_{sp}) is $$calculated using the concentrations of $$Ca^{2+}$$ and $$OH^-$$ ions. If $$[Ca$$^{2+}$$] = 0.01\,M$$ and $$[OH^-] = 0.02\,M$$, what is $$K_{sp}$$?

Accepted Answer

$$K_{sp} = [Ca$$^{2+}$$] 	imes [OH^-]^2 = 0.01 	imes (0.02)^2$ = 0.000004$$

Question 7

A calorimetry experiment measures the temperature change when 50.0 g of water absorbs 420 J of heat. What is the temperature change ($$\Delta T) of $$the water? (Specific heat of water $$c = 4.18\,J/g\cdot K)$$

Accepted Answer

$$\Delta T = \frac{420}{50 	imes 4.18} = 2.01\,K$$

Question 8

In a voltaic cell, the following reaction occurs: $$Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s). $$Which metal acts as the anode?

Accepted Answer

Zinc ($$Zn)$$

Question 9

A student adds hydrochloric acid ($$HCl) to a $$buffer solution containing $$CH_3COOH$$ and $$CH_3COONa. $$What happens to the pH of the solution?

Accepted Answer

The pH decreases slightly.

Question 10

In the Rate of Chemical Reactions experiment, the rate law for a reaction is determined to be $$rate = k[A]^2[B]. If$$ $$[A] is $$doubled and $$[B] is $$halved, how does the rate change?

Accepted Answer

The rate increases by a factor of 2.

Question 11

A solution contains $$Ca^{2+}$$ and $$OH^-$$ ions. If the concentration of $$OH^- is $$increased, what happens to the solubility of $$Ca(OH)_2$$?

Accepted Answer

The solubility decreases due to the common ion effect.

Question 12

In a calorimetry experiment, a student mixes 100 g of water at $$20^\circ C$$ with 100 g of water at $$80^\circ C. $$What is the final temperature, assuming no heat loss?

Accepted Answer

$$50^\circ C$$

Question 13

In the acid-base titration experiment, which indicator would be most appropriate for titrating a strong acid with a strong base?

Accepted Answer

Phenolphthalein (color change at pH 8-10)

Question 14

A voltaic cell is constructed with $$Ag^+/Ag$$ and $$Cu^{2+}/Cu$ half-cells. Given E$$^\circ_{Ag^+/Ag} = +0.80\,V$$ and E$$^\circ_{$$Cu^{2+}/Cu$$} = +0.34\,V$$, what is the standard cell potential?

Accepted Answer

$$E^\circ_{cell} = 0.80 - 0.34 = 0.46\,V$$

Question 15

In the Determination of Equilibrium Constant experiment, a student finds that increasing the temperature decreases the value of $$K_{eq}. $$What does this indicate about the reaction?

Accepted Answer

The reaction is exothermic.

Question 16

A buffer is made by mixing 0.1 M $$NH_3$$ and 0.1 M $$NH_4Cl. If $$the $$K_b$$ for $$NH_3 is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer? (pK_b$$ = -\log K_b$$; $$pOH = pK_b + \log \frac{[$$NH_4$$^+]}{[$$NH_3$$]}$$; pH = 14 - $$pOH$$)

Accepted Answer

$$pH = 14 - (4.74 + 0) = 9.26$$

Question 17

In a voltaic cell, electrons flow from the anode to the cathode. Which statement best describes the process occurring at the anode?

Accepted Answer

Oxidation occurs at the anode.

CHEM 1112 Final Exam Lab Concepts and Calculations Study Guide

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