CHEM CHAP 9

Balance the equation: Al (s) + H2SO4 (aq) --> Al2(SO4)3 (aq) + 3 H2 (g)

2 Al + 3 H2SO4 --> Al2(SO4)3 + 3 H2

Lithium metal reacts with water to form aqueous lithium hydroxide and hydrogen gas. Write a BALANCED chemical equation for the reaction, including ABBREVIATIONS for the physical states.

2 Li (s) + 2 H2O (l) --> 2 LiOH (aq) + H2 (g)

Balance the equation: Sb (s) + O2 (g) --> Sb2O3 (s)

4 Sb + 3 O2 --> 2 Sb2O3

How can you tell whether a chemical equation is balanced? What scientific principle is reflected in a balanced equation?

Both sides of the equation must have the same amount of atoms for each element. It has to be balanced because according to the Law of Conservation of Mass, matter can neither be created nor destroyed.

Explain why you cannot change a formula of a compound in a reaction in order to balance a chemical equation.

If you change the formula, you are changing the amount of atoms. You cannot alter the formula because it violates the Law of Conservation of matter and mass. It changes the identity of the compound.

Write the balanced equation for the following reaction: Magnesium metal, when reacted with aqueous hydrochloric acid, produces aqueous magnesium chloride and hydrogen gas

Mg (s) + 2 HCl (aq) --> MgCl2 (aq) + H2 (g)

The word equation "magnesium reacts with chlorine to produce magnesium chloride" would be represented by which of the following formula equations? a. Mg + Cl2 --> MgCl2 b. MgCl2 --> Mg + Cl2 c. MgCl2 + Mg --> Cl2 d. Mg --> Cl2 + MgCl2

Mg + Cl2 --> MgCl2

In a chemical reaction, what is the relationship between the total mass of the reactants and the total mass of the products? a. They must be equal. b. The mass of the reactants must be greater. c. The mass of the reactants must be greater. d. There is no general relationship between the two.

a. They must be equal

In a chemical equation, the number of molecules of a given substance is indicated by a a. coeffiecient b. subscript c. superscript d. reaction number

a. coefficient

In a chemical equation, the symbol that takes the place of the words "reacts with" is a(n) a. plus sign. b. coefficient c. equal sign d. arrow

a. plus sign

If no number is written to the left of a formula in a chemical equation, what number is assumed to be there? a. 0 b. 1 c. 1 X 10^23 d. 6.02 X 10^23

b. 1

HOW MANY of the following statements are true concerning chemical equations? I. Coefficients can be fractions. II. Subscripts can be fractions III. Coefficients represent the # of molecules of the reactants and products. IV. Changing the subscripts to balance an equation can only be done once. V. Atoms are conserved when balancing chemical reactions. a. 1 b. 2 c. 3 d. 4

b. 2

What number should be written in front of Na to balance the equation Na to MgCl2 --> NaCl + Mg a. 1 b. 2 c. 3 d. 4

b. 2

coefficients for KNO3? Pb(NO3)2 + K2CO3 --> PbCO3 + KNO3 a. 5 b. 2 c. 4 d.1

b. 2

A substance that enters into a chemical reaction is called a a. mole b. reactant c. coefficient d. product

b. reactant

To balance the equation HgO (s) --> Hg (l) + O2, what coefficient should be placed in front of the O2? a. 2 b. 1/2 c. 1 (understood) d. 6

c. 1 (understood)

All of the following are clues that a chemical reaction has taken place EXCEPT: a. a color change b. the reactant is smaller c. a solid forms d. bubbles form

c. a solid forms

In a chemical equation, the symbol that takes the place of the word "yields" is a(n) a. equal sign b. coefficient c. arrow d. plus sign

c. arrow

In balancing a chemical equation, which of the following are you allowed to do? a. change subscripts b. change superscripts c. write coefficients d. add new substances

c. write coefficients

Which of the following symbols means a substance is in water solution? a. (l) b. (s) c. (w) d. (aq)

d. (aq)

How many atoms of oxygen are represented in 2 Ca(NO3)2? a. 4 b. 6 c. 10 d. 12

d. 12

coefficients for HCL? MnO2 + HCL --> MnCl2 + Cl2 + H2O a. 1 b. 2 c. 3 d. 4

d. 4

coefficients for Fe? Al + Fe3O4 --> Al2O3 + Fe a. 1 b. 3 c. 6 d. 9

d. 9

In a reaction in which hydrogen reacts with oxygen to produce water, which substances are the reactants? a. hydrogen only b. oxygen only c. water d. both hydrogen and oxygen

d. both hydrogen and oxygen

A substance that is formed by a chemical reaction is called a a. mole. b. reactant. c. coefficient. d. product.

d. product

The symbol (s) written after a formula in a chemical equation stands for a. soluble. b. solution. c. synthesis. d. solid.

d. solid

When oxygen is available, sulfur dioxide is produced from the burning of sulfur. Which of the following word equations best represents this reaction? a. sulfur --> sulfur dioxide + oxygen b. sulfur dioxide + oxygen --> sulfur c. sulfur dioxide --> sulfur + oxygen d. sulfur + oxygen --> sulfur dioxide

d. sulfur + oxygen --> sulfur dioxide