Chemical Reactions Questions
Bring on the tough stuff
- List the different types of chemical reactions and give a brief description.
- Write the generic form of each type of chemical reaction.
- Give a specific example for each type of chemical reaction. Make sure the equations are properly balanced.
- State the type of reaction and balance it properly: NaOH + CaBr2 → Ca(OH)2 + NaBr.
- What is the Law of Conservation of Mass, and how does it relate to chemical reactions?
- When balancing a chemical equation, is it okay to adjust the subscript in a formula? Explain.
- State the type of reaction and balance it properly: C8H18 + O2 → CO2 + H2O.
- Predict the products that will result when these reactants combine and write a balanced chemical equation for each:
Fe + CuSO4 →
Br2 + MgCl2 →
Mg + AlCl3 →
- What is an activity series and how does it relate to chemical reactions?
- State the type of reaction and balance it properly: Pb(NO3)2+ AlCl3 → PbCl2 + Al(NO3)3.
Solutions
1. List the different types of chemical reactions and give a brief description.
Synthesis, decomposition, single displacement, and double displacement.
A synthesis reaction occurs when two elements or compounds combine to form a more complex molecule. A decomposition reaction is the opposite of a synthesis reaction, and occurs when a molecule breaks apart to form two elements or less complex molecules. Single displacement reactions occur when a single element reacts with a chemical compound and switches places with one of the elements in the compound. Double displacement reactions occur when the cations of two ionic compounds switch places.
2. Write the generic form of each type of chemical reaction.
Synthesis:
A + B → AB
Decomposition:
AB → A + B
Single displacement:
AB + C → AC + B
Double displacement:
AB + CD → AC + BD
3. Give a specific example for each type of chemical reaction. Make sure the equations are properly balanced.
Synthesis:
8 Fe + S8 → 8 FeS
Decomposition:
2 H2O2 → 2 H2 + O2
Single displacement:
Fe + CuSO4 → Cu + FeSO4
Double displacement:
AgNO3 + NaCl → AgCl + NaNO3
4. State the type of reaction and balance it properly: NaOH + CaBr2 → Ca(OH)2 + NaBr.
Double displacement: 2 NaOH + CaBr2 → Ca(OH)2 + 2NaBr
5. What is the Law of Conservation of Mass, and how does it relate to chemical reactions?
The Law of Conservation of Mass states that matter cannot be created nor destroyed. This means that all chemical reactions must be properly balanced so there are the same number and type of each atom on each side of the reaction arrow.
6. When balancing a chemical equation, is it okay to adjust the subscript in a formula? Explain.
It is absolutely NOT okay to adjust the subscript in a formula because changing the subscripts changes the chemical identity of the compound. Instead, only coefficients can be altered when balancing a chemical equation.
7. State the type of reaction and balance it properly: C8H18 + O2 → CO2 + H2O.
Combustion: 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
8. Predict the products that will result when these reactants combine and write a balanced chemical equation for each:
Fe + CuSO4 →
Br2 + MgCl2 →
Mg + AlCl3 →
Fe is above Cu in the activity series, therefore the first reaction will occur because Fe is more reactive than copper.
Fe + CuSO4 → FeSO4 + Cu
Cl is more reactive than Br because Br is listed below Cl in the activity series. This means no reaction will occur.
Mg is listed above Al in the activity series, therefore this reaction will occur because Mg is more reactive than Al.
3 Mg + 2 AlCl3 → 2 Al + 3 MgCl2
9. What is an activity series and how does it relate to chemical reactions?
An activity series is a list of metals (or halogens) in order of decreasing reactivity. It is used to predict which reaction will occur. For example, a metal with a higher activity will replace a metal with a lower activity in a single displacement reaction. The same is true for halogens.
10. State the type of reaction and balance it properly: Pb(NO3)2+ AlCl3 → PbCl2 + Al(NO3)3.
Double Displacement Reaction: 3 Pb(NO3)2+ 2 AlCl3 → 3 PbCl2 + 2 Al(NO3)3