BJU Physical Science Ch 7

Which of the following is not evidence that a chemical change has occurred?

• a change in color

• a change in size

• a distinct smell

• a change in temperature

Identify the correctly balanced chemical equation for the following word equation: Magnesium metal burns in gaseous oxygen to produce magnesium oxide.

• Mg + O₂ → 2MgO

• 2Mg + O₂ → 2MgO

• 2Mg + O₂ → MgO

• 2Mg + 2O₂ → 2MgO₂

What is a mole?

• an equation

• a mass

• a quantity

• a ratio

How many moles of hydrogen gas are needed for the following reaction? N₂ + 3H₂ → 2NH₃

• 1

• 2

• 3

• 6

A key feature of a single-replacement reaction is that

• a single reactant becomes two or more products.

• both reactants and products include an element and a compound.

• two compounds swap ions, producing two new compounds.

• two or more reactants become a single product.

Which of the following occur(s) in a redox reaction?

• An element loses electrons.

• An element gains electrons.

• both A and B

• neither A nor B

Which of the following does not happen to the energy given off by a campfire?

• A. Some energy is absorbed by the environment.

• B. Some energy is given off as light energy.

• C. Some energy is given off as thermal energy.

• D. Some energy is destroyed by combustion.

How does a catalyst increase a reaction rate?

• A. by increasing the concentration of the reactants

• B. by increasing the number of collisions

• C. by lowering the activation energy

• D. by lowering the surface area

What happens to the forward and reverse reactions when a system reaches its equilibrium state?

• A. Both the forward and reverse reactions stop.

• B. The forward and reverse reactions both continue to occur at the same rate.

• C. The forward reaction stops and the reverse reaction continues to occur.

• D. The reverse reaction stops and the forward reaction continues to occur.

Boiling water is an example of a chemical change.

• True

• False