1. Which of the following statements is true about reaction rates?
a. Reaction rates can be predicted from the coefficients of the balanced equation.
b. Reactants usually disappear faster than the products appear.
c. Reactants usually disappear slower than the products appear.
d. Reaction rates can only be determined by experimentation.
2. In general, a small decrease in the temperature of an exothermic reaction will
a.cause the reaction to go in reverse
b.cause the reaction to stop
c.cause an increase in the reaction rate
d. cause a decrease in the reaction rate
1 is d
2 is c
1. d. Reaction rates can only be determined by experimentation. Because you can't simply look at a balanced equation and predict the rate at which a reaction will occur. That would be like trying to predict the weather by looking at a banana peel.
2. a. Cause the reaction to go in reverse. Just like when you accidentally put your car in reverse instead of drive when trying to park and end up crashing into a lamppost. Except in this case, it's the reaction itself that's reversing, not your driving skills.
1. The correct statement is:
c. Reactants usually disappear slower than the products appear.
2. The correct answer is:
d. cause a decrease in the reaction rate.
To answer question 1, we need to determine which statement is true about reaction rates.
a. Reaction rates can be predicted from the coefficients of the balanced equation. This statement is not entirely true. The coefficients in a balanced equation represent the stoichiometry of the reaction, but they do not directly indicate the rate at which the reaction occurs. The rate of a reaction depends on various factors such as temperature, concentration, and catalysts.
b. Reactants usually disappear faster than the products appear. This statement is generally true. In most chemical reactions, reactants are consumed faster than products are formed. The rate of consumption of reactants typically exceeds the rate of product formation.
c. Reactants usually disappear slower than the products appear. This statement is not true. As mentioned earlier, reactants are generally consumed faster than products are formed.
d. Reaction rates can only be determined by experimentation. This statement is true. The rate of a chemical reaction can only be determined through experimental measurements. Various methods like monitoring changes in concentration or recording changes in physical properties of the system over time can be used to determine reaction rates.
Therefore, the correct answer to question 1 is b. Reactants usually disappear faster than the products appear.
Moving on to question 2, we need to determine the effect of a small decrease in temperature on an exothermic reaction.
a. A small decrease in temperature causing the reaction to go in reverse is not correct because exothermic reactions release energy. Decreasing the temperature typically reduces the rate at which the reaction proceeds, but it does not cause the reaction to reverse.
b. A small decrease in temperature does not cause the reaction to stop. The reaction may slow down, but it does not come to a complete stop unless the temperature is significantly reduced.
c. A small decrease in temperature generally leads to a decrease in the reaction rate because exothermic reactions are favored by higher temperatures. Lowering the temperature slows down the reaction rate.
d. The correct answer is d. A small decrease in temperature causes a decrease in the reaction rate. Lower temperatures usually restrict the motion of molecules, leading to a decrease in collisions and, therefore, a decrease in the reaction rate of an exothermic reaction.
Therefore, the correct answer to question 2 is d. A small decrease in the temperature of an exothermic reaction causes a decrease in the reaction rate.