Chem Summ

Question 1

The figure on the right represents an electrolytic cell. Which of the followings statements is TRUE about ELECTROLYTIC cells?
a. Electrons flow from the cathode to the anode in the external circuit
b. The redox reaction involved in such a cell is spontaneous
c. Oxidation occurs at the cathode.
d. Reduction occurs at the cathode.

Answer 1

d. Reduction occurs at the cathode.

Question 2

The reaction below shows the electrolysis of water. Which statements correctly describe the information below?

I. The electrolysis of water produces hydrogen and oxygen gases.
II. At the anode, water is reduced to hydrogen gas and hydroxide ions.
III. At the cathode, water is oxidized to oxygen gas and hydrogen ions.

Answer 2

I only.

I. The electrolysis of water produces hydrogen and oxygen gases.

Question 3

Blood itself tends to be a buffer solution by keeping its pH value constant. Buffer solutions help in the adjustment of the nature of blood. Which of the statements below may CORRECTLY describe the role of buffers in our body?

Statement 1: If the alkaline nature of blood increases, buffer solutions tend to increase the pH value of blood.
Statement 2: If the blood becomes acidic, buffer solutions increase the pH value of blood.

Answer 3

Only statement 2 is correct.

Statement 2: If the blood becomes acidic, buffer solutions increase the pH value of blood.

Question 4

Consider the equilibrium reaction
C2H5OH + CH3COOH <-> CH3COOC2H5 + H2O

What effect will likely occur if a catalyst is added on this reaction?

a. Less H2O is formed.
b. More C2H5OH is formed.
c. More CH3COOC2H5 is formed.
d. The system reaches equilibrium faster.

Answer 4

d. The system reaches equilibrium faster.

Question 5

In a 1-Liter container, the amount of H2 is 1.0 mole, the amount of I2 is 2.0 moles & the amount of HI is 2.0 moles at equilibrium. Below is the balanced chemical equation for this reaction: H2 (g) + I2(g) <-> 2HI(g).
What is Kc for this reaction?

a. 1.0
b. 1.3
c. 2.0
d. 2.3

Answer 5

c. 2.0

Question 6

The equilibrium constant, Kc is 49 at a fixed temperature. Two moles of hydrogen and two moles of iodine are allowed to reach equilibrium at this temperature. What is the concentration of hydrogen iodide at equilibrium? Refer to the chemical equation in the previous question (#5).

a. 0.77
b. 1.55
c. 1.75
d. 9.20

Answer 6

b. 1.55

Question 7

An electrochemical cell is constructed using electrodes based on the following half reactions:
Ni(s) -> Ni^2+(aq) + 2e- Eo = -0.257V
Au^3+(aq) + 3e- -> Au(s) Eo = +1.498V

Which is the cathode and anode in this cell respectively?

a. Au^3+, Au^3+
b. Au^3+, Ni
c. Ni, Au^3+
d. Ni, Ni

Answer 7

b. Au^3+, Ni

Question 8

An electrochemical cell is constructed using electrodes based on the following half reactions:
Ni(s) -> Ni^2+(aq) + 2e- Eo = -0.257V
Au^3+(aq) + 3e- -> Au(s) Eo = +1.498V

What is the standard cell potential?
a. +1.755 V
b. -1.755 V
c. +1.241 V
d. -1.241 V

Answer 8

a. +1.755 V

Question 9

For the synthesis of ammonia at 500C, N2(g) + 3H2(g) <-> 2NH3(g), the equilibrium constant is 6.0 x 10^-2. Predict the direction in which the system will shift to reach equilibrium if [NH3]0 = 1.0 x 10^-3 M; [N2]0 = 1.0 x 10^-5 M; [H2]0 = 2.0 x 10^-3 M

a. No shift
b. Right the left
c. Shift to left
d. Shift to right

Answer 9

c. Shift to left

Question 10

[Two water molecules are able to react with other forms to form a hydronium ion and a hydroxide ion. This is known as the self-ionization of water. Using the concentrations of ions produced. it is possible to determine the equilibrium constant for the ionization of water, also known as the ion-product constant of water.]

Which of the following equations represent the ion-product constant of water?

a. Kw = [H3O+][OH-]
b. Kw = [H3O+] / [OH-]
c. Kw = [H3O+] + [OH-]
Kw = [H3O+] - [OH-]

Answer 10

a. Kw = [H3O+][OH-]

Question 11

[Two water molecules are able to react with other forms to form a hydronium ion and a hydroxide ion. This is known as the self-ionization of water. Using the concentrations of ions produced. it is possible to determine the equilibrium constant for the ionization of water, also known as the ion-product constant of water.]

What is the value of Kw if the sample of water has a pH of 7.30?
a. 1.012 x 10^-15
b. 2.512 x 10^-15
c. 5.015 x 10^-15
d. 5.030 x 10^-15

Answer 11

b. 2.512 x 10^-15

Question 12

The diagram on the right shows the concentration of hydrogen, iodine, and hydrogen iodide for the reaction between hydrogen and iodine. Which of the following statements is INCORRECT?

a. At point C, the system is in a state of dynamic equilibrium.
b. The reaction between the gases reaches equilibrium at point C.
c. Adding more hydrogen at point D will alter the shape of the graph.
d. At point A on the time axis, the concentration of all three gases is zero.

Answer 12

d. At point A on the time axis, the concentration of all three gases is zero.

Question 13

The pOH of a solution of NaOH is 11.30. What is the [H+] for this solution?
a. 2.0 x 10^-3
b. 2.5 x 10^-3
c. 5.0 x 10^-12
d. 4.0 x 10^-12

Answer 13

a. 2.0 x 10^-3

Question 14

The value of Kw at 10C is 2.95 x 10^-15

What is the [H3O+] at this temperature?
a. 3.5 x 10^-8
b. 4.8 x 10^-8
c. 5.4 x 10^-8
d. 6.6 x 10^-8

Answer 14

c. 5.4 x 10^-8

Question 15

The value of Kw at 10C is 2.95 x 10^-15

What is the pOH of water at this temperature?
a. 6.6
b. 7.3
c. 8.6
d. 9.3

Answer 15

b. 7.3

Question 16

A buffer solution has a pH of 4.87. If the buffer contains a weak acid (Ka = 3.30 x 10^-5), What is the [conjugate base] / [weak acid] ratio?

a. 0.41
b. 2.45
c. 4.48
d. 4.87

Answer 16

b. 2.45

Question 17

Which of the following chemical systems at equilibrium involves water acting as a Bronsted-Lowry acid?

(nakakatamad isulat choicec :P)

Answer 17

a. SO4^-2 + H3O^+ <-> HSO4^- + H2O

Question 18

The Eo value if Ni^2+ / Ni is -0.25V and Ag^+ / Ag is +0.80V. If a cell is made by taking the two electrodes, what is the feasibility of the reaction?

Answer 18

b. Since Eo value for the cell will be positive, redox reaction is feasible.

Question 19

The concentration of H3O^+ in a patient’s blood sample is 11.65 x 10^-8 M. Is the blood acidic, basic, or neutral?
a. Strongly basic
b. Strongly acidic
c. Slightly acidic
d. Slightly basic

Answer 19

c. Slightly acidic

Question 20

The electrolytic process is widely used in various industrial applications. One major application of this process is the extraction of pure metal from their ores (electro-extraction). Below is a series of steps on how to conduct electro-extraction. Which one is NOT included?

Answer 20

b. the resulting solution is heated

Question 21

Which change will increase the equilibrium concentration of sulfur trioxide in this reaction?
2SO2(g) + O2(g) <-> 2SO3(g), deltaH = negative
a. Using a catalyst
b. Increasing the pressure
c. Increasing the temperature
d. Decreasing the concentration of oxygen

Answer 21

b. Increasing the pressure

Question 22

What will happen to the position of equilibrium and the value of the equilibrium constant when the temperature is increased in the following reaction?

Br2(g) + Cl2(g) <-> 2BrCl(g), deltaH = +14kJ

Answer 22

c. Equilibrium shifts towards the products and the equilibrium constant increases.

Question 23

Henri Le Chatelier studied equilibrium reactions in industry in the late 19th century. According to Le Chatelier’s principle, what effect would an increase in pressure have on the yield of ammonia at equilibrium?

Answer 23

c. There would be a greater yield of ammonia

Question 24

Which of the following statements regarding the Gibbs free energy change for a reaction is FALSE?

Answer 24

a. The Gibbs free energy change is the proportion of the enthalpy chance of a reaction that is used to increase the entropy.

Question 25

What is the conjugate base of the HSO4^- (aq) ion?
a. H2SO4(aq)
b. SO4^2-(aq)
c. H3O^+ (aq)
d. H2O(l)

Answer 25

b. SO4^2-(aq)

Question 26

An unknown substance acts as an acid and as a base depending on the reaction’s circumstances. What properties do this unknown substance possess to achieve its role?
I. donates electrons when reacting with an acid.
II. donates its protons when reacting with a base.
III. accepts electrons when reacting with a base.
IV. accepts protons when reacting with an acid.

Answer 26

II. donates its protons when reacting with a base.
&
IV. accepts protons when reacting with an acid.

Question 27

The nature of buffers is to maintain the pH of the solution relatively stable. What comprise buffers to attain this?

Answer 27

c. Weak acid and their conjugate base

Question 28

Corrosion is a reduction-oxidation reaction in which the metal is being oxidized by its surroundings. As the lead acid battery runs, the sulfuric acid releases hydrogen gas. The gas then mixes with the air around it. The chemical reaction that takes place as hydrogen gas collides with the air, moisture and salt causes corrosion. What are the preventive measures to slow down this phenomenon?

Answer 28

I. Coat your battery terminals with dielectric grease or battery terminal protector.
II. Make sure your the battery is stored in a moderate temperature environment.
IV. Check for leaking fluids

Question 29

Which of the following is ALWAYS positive when a spontaneous process.
a. deltaH universe
b. deltaH surrounding
c. deltaS surrounding
d. deltaS universe

Answer 29

d. deltaS universe

Question 30

In which of the following compound does nitrogen have the most positive oxidation state?
a. Ammonia
b. Nitric Acid
c. Nitrogen Dioxide
d. Nitrogen Gas

Answer 30

b. Nitric Acid

Question 31

What is the concentration of OH^- ions in the blood for the last question?

Answer 31

d. 8.51 x 10^-8

Question 32

A few drops of concentrated sulphuric acid were added to a mixture of 0.1 mol of methanol and 0.2 mol of ethanoic acid. Even after a considerable time, the reaction mixture was found to contain some of each reactant. Which of the following is the BEST explanation for the incomplete reaction?

Answer 32

a. An equilibrium mixture was formed