Working with half lives to determine the time required to reach a certain percentage of its initial concentration.

A first order reaction has a half-life of 157 seconds. How much time is required for the reactant to be reduced to 12.5% of its initial concentration?

Identifying a catalyst in a reaction.

The elementary steps for the catalyzed decomposition for dinitrogen monoxide are shown below. Identify the catalyst. NO(g)+N2O(g)--->N2(g)+NO2(g) 2NO2(g)-->2NO(g)+O2(g)

Calculating the change in the rate constant when temperature is decreased.

For a certain reaction, the activation energy is 52.1kJ/mole. By what ratio will the rate constant change if the temperature is decreased from 175 degrees Celsius to 75 degrees Celsius?

Calculating the time required for a reaction to be reduced by a certain percentage given the half life.

A first order reaction has a half-life of 2.10 hours. How much time is required for the reactant to be reduced to 33.0% of its initial concentration?

Calculating the partial pressure of a gas at equilibrium given the equilibrium constant.

At a given temperature, the equilibrium constant (Kp) for the decomposition of dinitrogen dioxide is 0.172. If 0.224atm N2O4 is sealed in a flask, what partial pressure of NO2 will exist at equilibrium?