Chemical Reactions Quiz

The energy that enters or leaves a system during a chemical reaction comes from-

• the building and breaking of chemical bonds

• the conversion of mass to energy

• heat absorbed from the surroundings

• the kinetic energy of electron motion

All of the observations are evidence of a chemical change except-

• observation I

• observation II

• observation III

• observation IV

Which of the following is the most reliable indicator that the final mixture is completely neutralized?

• The reaction produces water and a salt of some kind

• The pH of the final mixture is zero

• The final pH is halfway between the pH values for both reactants

• There are no excess hydrogen or hydroxide ions

What data do we need in order to determine whether the reaction absorbed or released thermal energy?

• The mass of the substances before and after the reaction

• The temperature inside the beaker before and after the reaction

• Whether or not light and sound were produced during the reaction

• How long it took for the reaction to take place once the chemicals combined

Leah tested an unknown substance and recorded her observations listed in the picture. From her observations, Leah can conclude that the unknown substance is-

• salt

• a base

• water

• an acid

Which of the following is not a sign of a chemical reaction taking place?

• Change in color

• Formation of a precipitate

• Change in temperature

• Change in volume

What is the primary factor that determines whether a reaction is endothermic or exothermic?

• The type of reactants involved

• The amount of heat absorbed or released

• The speed of the reaction

• The presence of a catalyst

Which of the following statements is true about the conservation of mass in a chemical reaction?

• Mass is always conserved in a chemical reaction

• Mass is only conserved in exothermic reactions

• Mass is only conserved in endothermic reactions

• Mass is not conserved in a chemical reaction