Balancing Chemical Equations
Balance this Equation:
Na + Cl2 -> NaCl
2Na + Cl2 -> 2NaCl
Which of the following is NOT an example of a chemical reaction?
a. milk turning sour
b. food being digested
c. a match burning
d. ice melting
d. ice melting
A shorthand notation that represents a compound or diatomic molecule is called a(n) _____________.
chemical formula
In which kind of chemical reaction do two or more substances combine to form one new compound?
a. synthesis
b. decomposition
c. single-displacement
d. double-displacement
a. synthesis
Ag2O -> Ag + O2
2Ag2O -> 4Ag + O2
CO2 + H2O + energy -> C6H12O6 + O2
6CO2 + 6H2O + energy -> C6H12O6 + 6O2
Which of the following is an example of a diatomic molecule?
a. NaCl
b. O2
c. Mg
d. CaCl2
b. O2
The minimum amount of energy needed to start a reaction is called _____________.
activation energy
Which of the following usually increases the rate of a reaction?
a. decreasing the concentration of the reactants
b. grinding a solid reactant into a powder
c. lower the temperature of the reactants
d. raising the temperature of the products
b. grinding a solid reactant into powder
NaBr + CaF2 -> NaF + CaBr2
2NaBr + CaF2 -> 2NaF + CaBr2
H2CO3 -> H2O + CO2
H2CO3 -> H2O + CO2
For a chemical bond to break,
a. individual atoms must be present
b. energy is required
c. covalent compounds must be mixed
d. solids must be dissolved
b. energy is required
In a(n) ________________ reaction, ions in different compounds switch places.
double-displacement
Which of the following is an example of a chemical reaction?
a. a tire losing air
b. water boiling
c. a solid forming in solution
d. ice melting
c. a solid forming in solution
S8 + O2 -> SO3
S8 + 12O2 -> 8SO3
Zn + HCl -> ZnCl2 + H2
Zn + 2HCl -> ZnCl2 + H2
Which of the following phrases describes a catalyst?
a. slows the rate of a reaction
b. increases the energy given off by a reaction
c. lowers the activation energy of a reaction
d. changes permanently when used in a reaction
c. lowers the activation energy of a reaction
In a chemical formula, if no _________ is written after an element, then only one atom of the element is present.
subscript
How can the rate of reaction be increased?
a. by decreasing the concentration of the reactants
b. by grinding a solid reactant into a powder
c. by lowering the temperature of the reactants
d. by raising the temperature of the products
b. by grinding a solid reactant into a powder
CH4 + O2 -> CO2 + H2O
CH4 + 2O2 -> CO2 + 2H2O
Pb(OH)2 + HCl -> H2O + PbCl2
Pb(OH)2 + 2HCl -> 2H2O + PbCl2
Why does the law of conservation of mass dictate that chemical equations be balanced?
a. because atoms are never gained or lost in a chemical reaction
b. because elements are classified by weight
c. because chemical formulas are written from left to right
d. because using the wrong chemical symbol causes confusion
a. because atoms are never gained or lost in a chemical reaction
A substance that slows down or stops a chemical reaction is called a(n) ______________.
inhibitor
Which of the following equations is an example of a single-displacement reaction?
a. Fe + 2HCl -> FeCl2 + H2
b. 2Mg + O2 -> 2MgO
c. 2H2O2 -> 2H2O + O2
d. NaOH + HCl -> NaCl + H2O
a. Fe + 2HCl -> FeCl2 + H2
C3H8 + O2 -> CO2 + H2O
2C3H8 + 25O2 -> 16CO2 + 18H2O