1. Mitch weighs out 67 grams of potassium (K) to make a buffer. How many moles of potassium did Dr. Hellman weigh out?

2. Which statement is NOT true about a reaction rate?

Group of answer choices

Increases with increase in reactant concentration

Increases with increasing temperature

Is the speed at which product is formed

Is the rate at which reactant is used up

All of the answers are true

3. Which statement is NOT true about a catalyst?

Group of answer choices

Are not used up during a reaction

Increases the rate of the reaction

Lowers the energy of activation

Biological catalysts are called enzymes

Are used up during a reaction

1. 1.72 moles of potassium.

2. All of the answers are true

3. Are used up during a reaction

Explanation:

Recall that the number of moles is obtained from;

Number of moles = Mass of potassium / molar mass of potassium

Mass of potassium = 67 g

Molar mass of potassium = 39 gmol-1

Number of moles of K = 67 g / 39 gmol-1

Number of moles = 1.72 moles of potassium.

2. When we look at all the options, we will realize that all the options are true. The rate of reaction doubles for each 10°C rise in temperature, increasing reactant concentration increases particle collision and ultimately increases the rate of reaction. Rate of reaction deals with rate of disappearance of reactants or rate of appearance of products.

3. Catalysts remain unchanged in a chemical reaction because they do not actually participate in the reaction. Hence they are not used up in any chemical reaction.