Chemical Reaction Rates and Stoichiometry

The video tutorial explains reaction rates and how stoichiometry helps relate the rates of appearance and disappearance of species in a chemical reaction. It covers the change in concentration of reactants and products over time, using stoichiometry to calculate rates for different species. An example reaction is given, showing how coefficients affect reaction rates. The oxidation of ammonia is used to demonstrate rate expressions and calculations for the formation of nitrogen, water, and the consumption of ammonia. The tutorial concludes with a summary of how stoichiometry determines the rate of change in reactant and product concentrations.

What typically happens to the concentration of reactants during a chemical reaction?

• It fluctuates randomly.

• It remains constant.

• It decreases.

• It increases.

How can stoichiometry help in a chemical reaction?

• By predicting the temperature change.

• By relating the rates of different species.

• By determining the pH level.

• By changing the color of reactants.

In the reaction A + B → C, why do the rates of A and B have a negative sign?

• Because they are being formed.

• Because they are inert.

• Because they are being used up.

• Because they are catalysts.

What happens to the rate of B if it has a coefficient of 3 in the reaction A + 3B → 2C?

• It remains constant.

• It decreases three times as fast as A.

• It decreases at the same rate as A.

• It increases three times as fast as A.

How do you adjust the rate expression for a species with a coefficient in a reaction?

• Add the coefficient to the rate.

• Divide the rate by the coefficient.

• Subtract the coefficient from the rate.

• Multiply the rate by the coefficient.

In the oxidation of ammonia, what is the first step in writing the rate expression?

• Calculate the pH level.

• Measure the temperature change.

• Look at the coefficients of each species.

• Identify the limiting reactant.

If the rate of formation of nitrogen is 0.27 moles per liter per second, what is the rate of formation of water?

• 1.08 moles per liter per second

• 0.81 moles per liter per second

• 0.54 moles per liter per second

• 0.27 moles per liter per second

What is the rate of disappearance of ammonia if the rate of formation of nitrogen is 0.27 moles per liter per second?

• 1.08 moles per liter per second

• 0.54 moles per liter per second

• 0.27 moles per liter per second

• 0.81 moles per liter per second

Why is the rate of disappearance of ammonia expressed with a negative sign?

• Because ammonia is inert.

• Because ammonia is a catalyst.

• Because ammonia is being formed.

• Because ammonia is disappearing.

What determines the rate of change of reactant and product concentrations in a reaction?

• The color of the reactants.

• The temperature of the reaction.

• The pressure of the system.

• The stoichiometry of the balanced equation.