Pet Lab Exam Practice Questions

The table below shows the concentration of reactants A and B in units of M and the initial rate of the reaction in units of M * min^-1.

 Determine the rate law. (no need value for k)

• Rate = k[A][B]²

• Rate = k[A][B]

• Rate = k[A][B]³

• Rate = k[A][B]⁴

The table below shows the concentration of reactants A and B in units of M and the initial rate of the reaction in units of M * min^-1.

Calculate the value of the rate constant

 

• 50 M^-2 min^-1

• 60 M^-1 min^-1

• 120 M^-3 min^-1

• 70 min^-1

The rate of the following reaction in aqueous solution is monitored by measuring the number of moles of mercury(II) chloride (Hg2Cl2) that precipitate per liter per minute. The data obtained are listed in the table.

1. Determine the order of reaction with respect to mercury(II) chloride, HgCl2. 

• Zero order

• First order

• Second order

• Third order

1. Which of the following statements is FALSE? 

• 1. The concentration of the products appears in the rate law.

• The orders of each reactant are determined experimentally.

• 1. The orders of each reactant are not necessarily the same as the stoichiometric coefficient.

• 1. The order of each reactant can have a negative value or even a fraction.

1. Which of the following equations best represents the half-life for zero-order reaction?

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1. The following reaction is second order in A:  A → product

At a certain temperature, the second-order rate constant is 1.46 M-1⋅s-1. Calculate the half-life of the reaction if the initial concentration of A is 0.86 M.

• 0.20 s

• 0.80s

• 1.23 s
• 0.6849 s

1. Consider the reaction:     A --> B

What is the correct expression for the rate of disappearance per unit time?

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1. What is the effect of temperature in chemical equilibrium?

• 1. As you increase the temperature the equilibrium shifts from left to right.

• As you increase the temperature the equilibrium shifts from right to left.

• 1. As you decrease the temperature the equilibrium shifts from left to right.

• none of the above

1. In the copper-ammonia complex, to return the blue color, how much hydrochloric acid is needed?

• 1. Equal the amount of ammonia added.

• 1. Double of the amount of ammonia added.

• 1. Half of the amount of ammonia added.

• 1. 1/3 of the amount of ammonia added.

1. Why did the solution become colorless when hydrochloric acid was added? 

• 1. The HCl reacted with ammonia (NH₃) to form a colorless complex. 

• 1. The addition of HCl increased the concentration of copper ions in the solution. 

• 1. HCl introduced excess chloride ions (Cl-) which competed with ammonia for copper ions, leading to the dissolution of the complex [Cu(NH3)4]2+

• 1. HCl reacted with water to produce a colorless byproduct.