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Chemical Reactions: Study Guide

 

Describe how the vocabulary terms in the following pairs are related to each other.

 

  1. Reactant; Product

Bonds are broken in reactants, and new bonds are formed in the products.

Reactants -yield-> Products

 

  1. law of conservation of mass; chemical reaction

The law of conservation of mass (Lavoisier) states, “In a chemical reaction, atoms are neither created nor destroyed.”

 

  1. color change; formation of precipitate

You can tell a chemical reaction has occurred when there has been a change in color or temperature or the formation of a precipitate or a gas.

 

 

  1. activation energy; catalyst

A catalyst decreases the amount of energy needed to start the reaction. Activation energy is the energy needed to start a chemical reaction.

 

 

Multiple Choice

In the blank to the left, write the letter of the choice that best completes each statement.

 

__D__5. During a chemical reaction, reactants always,

a.      become more complex

b.      require catalysts.

c.       lose mass.

d.      form products

__B__6. The splitting of water molecules into hydrogen and oxygen is an example of a

a.      combination reaction.

b.      chemical change.

c.       synthesis reaction.

d.      physical change.

____D__7. Combustion reactions:

a.      destroy atoms

b.      require glucose

c.       form precipitates

d.      require oxygen

__B__8. Which of the following will slow down the time of the reaction?

a.      breaking solid reactants into smaller pieces

b.      removing a catalyst

c.       increasing the temperature

d.      decreasing the concentration

__B__9. What does a catalyst do in a chemical reaction?

a.      It slows the reaction down.

b.      It speeds the reaction up.

c.       It becomes a product.

d.      It is a reactant.

_D___10. During a chemical reaction, the total amount of mass present


a.      increases

b.      decreases

c.       may increase or decrease

d.      does not change

_B___11. A chemical reaction must

a.      show energy

b.      be balanced

c.       use subscripts

d.      use coefficients

 

Balancing Equations

Balance the equation and write the correct coefficients in the equation.

 

12. 2 NaBr   +   Cl2 ->  2NaCl  +  Br2

 

14.  2Ag    +   H2S ->  Ag2S  + H2

13. 2 H2O  -> O2   + 2 H2

 

15.  CH4  +  2O2  ->   CO2 +2H2O

 

 

 

Discussion

Answer on a another sheet of paper

 

16. What are the factors that affect the rate of a chemical reaction? Four factors can change the rate of a chemical reaction.

1.the concentration of reactants

2.the surface area of reactants

3.the temperature of the reactant mixture

4.the presence of a catalyst.

 

17. When you balance a chemical equation, why can you change coefficients of reactants and products, but not subscripts? You cannot create or destroy matter.

 

18. A chemical equation is composed of what two items? Products and Reactants

 

20. Describe the difference between physical and chemical changes how can they be identified? Substances change in two ways.

physical changes. the substance does not change, but its properties can.

chemical changes. a substance changes into different substances. You can tell a chemical reaction has occurred when: change in color or temperature or the formation of a precipitate or a gas.