Phys & Chem Reactions
What is a physical reaction? Give an example.
A reaction in which form changes, but not the actual substance. A phase change is an example.
Balance this equation and determine what type of chemical reaction it is:
_ CH2O + _ H2 --> _ CH3OH
Synthesis
It's already balanced LOL
Why must equations be balanced? Define the law that this aligns with.
Law of conservation of energy --> matter cannot be created or destroyed; it can only change form
The amount and type of matter in the reactants must match the products. The bonds are just rearranged to create new substances.
_ C4H6O3 + _ H2O → _ C2H4O2
C4H6O3 + H2O → 2C2H4O2
_ Fe + _ H2SO4 --> _ Fe2(SO4)3 + _ H2
2Fe + 3H2SO4 --> Fe2(SO4)3 + 3H2
Define chemical reaction and give an example.
A reaction in which a new substance is formed (chemical bonds are rearranged). Photosynthesis (the creation of glucose from water and carbon dioxide) is an example.
Balance and determine type of reaction:
_ PCl3 --> _ P4 + _ Cl2
Decomposition
4PCl3 --> P4 + 6Cl2
What type of reaction was our glow stick lab an example of? Explain.
Exothermic --> the energy released was light
_ Fe + _ O2 --> _ Fe2O3
4Fe + 3O2 --> 2Fe2O3
_ C2H6 + _ O2 --> _ H2O + _ CO2
2C2H6 + 7O2 --> 6H2O + 4CO2
Change in color --> "clean" penny; phenolphthalein & basic solution
Formation of a gas --> baking soda & vinegar
Balance and determine type of reaction:
_ AgNO3 + _ Cu --> _ Cu(NO3)2 + _ Ag
Single Replacement
2AgNO3 + Cu --> Cu(NO3)2 + 2Ag
Which of the following are required for combustion to take place:
A. Only oxygen
B. Only carbon dioxide
C. Only fuel
D. All of the above
E. A & B
F. A & C
G. None of the above
F
_ C7H9 + _ HNO3 --> _ C7H6(NO2)3 + _ H2O
C7H9 + 3HNO3 --> C7H6(NO2)3 + 3H2O
_ H3PO4 + _ HCl --> _ PCl5 + _ H2O
H3PO4 + 5HCl --> PCl5 + 4H2O
Calcium carbonate, baking soda, and water exhibit two signs of a chemical change. What are they?
1. Formation of a gas (bubbling/fizzing)
2. Gain/release of energy
Balance and determine type of reaction:
_ C3H8 + _ O2 --> _ CO2 + _ H2O
Combustion
C3H8 + 5O2 --> 3CO2 + 4H2O
Which of the following are chemical reactions?
A. Digestion of food
B. Metal rusting
C. Photosynthesis
D. Melting Ice
E. A & C
F. A & D
G. A, B, & C
H. None of the above
I. All of the above
G
_ H2SiCl2 + _ H2O --> _ H8Si4O4 + _ HCl
4H2SiCl2 + 4H2O --> H8Si4O4 + 8HCl
_ CO + _ H2 --> _ C8H18 + _ H2O
8CO + 17H2 --> C8H18 + 8H2O
Define endothermic and exothermic reaction. What happens to the surrounding environment during these reactions?
Endothermic --> energy is absorbed by the reaction (products have more energy than reactants); the surrounding environment loses energy and becomes colder
Exothermic --> energy is released by the reaction (products have less energy than reactants); the surround environment becomes warmer
Balance and determine type of reaction:
_ KI + _ Pb(NO3)2 → _ KNO3 + _ PbI2
Double Replacement
2KI + Pb(NO3)2 → 2KNO3 + PbI2
Explain how a combustion reaction works.
A combustion reaction is an exothermic reaction in which a fuel is oxidized resulting in the release of energy. Carbon dioxide and water are a biproduct.
_ HSiCl3 + _ H2O --> _ H10Si10O15 + _ HCl
10HSiCl3 + 15H2O --> H10Si10O15 + 30HCl
_ HClO4 + _ P4O10 --> _ H3PO4 + _ Cl2O7
12HClO4 + P4O10 --> 4H3PO4 + 6Cl2O7