Name ______Date______
MYP Chemistry Unit 4 – Chemical Reactions
Types of Reactions Lab Activity
Aim: To write balanced equations & identify the types of reactions for the experiments you perform in the lab.
Background Information
There are an infinite number of chemical reactions. Chemist have divided these into broad classifications based on certain criteria. The classifications we will be identifying in lab today are synthesis, decomposition, single replacement, double replacement, and combustion. Note that some reactions will fall into more than one classification.
Reactions are described with chemical equations. A chemical equation is the symbolic representation of the chemicals involved in the reaction. These chemical equations can be used to describe both physical processes and chemical reactions. All chemical equations consist of reactants, the starting materials, products, the ending materials, the state of matter that the materials are in and a reaction arrow representing that a reaction has occurred.
Reactants →Products
The states of matter are symbolized by subscripts which follow each chemical. The most common states of matter are solid, liquid, gas and aqueous. The first three should be self-explanatory the final, aqueous, occurs when a substance is dissolved in water. Gases and ions are commonly found in an aqueous state. The symbols are as follows; solid (s), liquid (l), gas (g) and aqueous (aq).
Here are two examples of chemical equations:
H2O(s) → H2O(l)
CH4(g) + O2(g)→ CO2(g) + H2O(g)
The first is the physical process of ice melting the second is the combustion of methane gas. There is one other aspect necessary in writing a proper chemical equation; the equation must have the same number of each type atom on each side of the reaction arrow. The is due to the Law of Conservation of Matter; in other words you are not allowed to create or destroy matter. The first of the two above equations is fine, two hydrogens on each side and one oxygen on each side. The second equation needs to be balanced. This can be accomplished by placing a 2 in front of both the O2(g) and the H2O(g).
CH4(g) + 2 O2(g)→ CO2(g) + 2 H2O(g)
On each side, we find one carbon, four hydrogens and four oxygens. This equation obeys the conservation of matter and is said to be balanced.
Occasionally you may see something written above or below the arrow. This is normally a catalyst; platinum and nickel are a common metal catalysts. Another possibility is that the something is an environmental necessity, for example, heat or ultra violet light.
2 CO(g) + O2(g) 2 CO2(g)
The above chemical equation occurs in an automobiles catalytic converter, converting carbon monoxide into carbon dioxide in the presences of a platinum catalyst. The platinum is the reason the catalytic converter is expensive.
Descriptions and examples of each type of reaction follow:
Combination (Synthesis) reactions, two or more reactants combine to form one product. The general equation is:
A + B → C
A specific example is the tarnishing of a silver tea set:
Ag(s) + O2(g) → Ag2O(s)
Decomposition reactions, one reactant breaks to form two or more products. The general equation is:
A → B + C
A specific example is the electrolysis of water, electricity is causes this reaction:
2 H2O(l) 2 H2(g) + O2(g)
Single replacement reactions, one chemical replace another in a compound. The general equation is:
A + BX → B + AX
A specific example is zinc metal replacing iron in the iron(III) oxide compound, ships use this reaction to keep their hulls from rusting.
3 Zn(s) + Fe2O3(s) → 2 Fe(s) + 3 ZnO(s)
Double replacement reactions, chemicals in each of two compounds switch compounds. The general equation is:
AB + CD → AD + CB
A specific example is allows for the removal of toxic barium from a water source by adding a compound containing sulfate.
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)
Safety Precautions: Google and aprons must be worn at all stations. Be sure to dispose of all chemicals per instructions at each station. Do NOT mix anything except according to the procedure at each station.
Procedure:
1. Perform each reaction according to the directions embedded within Table 1 below and posted at each station.
2. If you see no immediate evidence of reaction, set the test tube aside for a few minutes, then re-examine.
3. Complete the equation for each reaction that occurs in the first column, making sure to balance it as well. If there is no evidence of reaction, write the words “no reaction” to the right of the arrow.
4. Work efficiently so that your group will be ready to move to the next station when time is called.
Table 1. Reactions and observations.
Chemical Reactants & Products / Observations Before Reaction / Observations After Reaction / Type of reaction1. ___Mg + ___ HCl → ______
Place a piece of magnesium ribbon in test tube. Add 5-8 drops of 6M HCl & observe. Pour the contents of the tube into the waste beaker; rinse the test tube.
2. ___CaCl2 + ___ Na2CO3→______
Put 5 drops of calcium chloridesolution in test tube. Add 5 drops of sodium carbonatesolution & observe. Pour the contents of the tube down the sink; rinse the test tube.
3. ___Zn + ___ HCl →______
Place a piece of zinc metal in test tube. Add 5-8 drops of 6M HCl & observe. Pour the contents of the tube into the waste beaker; rinse the test tube.
4. ___NaHCO3 + ___ HCl →______
Put a pinch of sodium hydrogen carbonate in test tube. Add 10 drops of 6M HCl & observe. Pour the contents of the tube down the sink; rinse the test tube.
5. ___Zn + ___CuCl2→______
Place a piece of zinc metal in test tube. Add 10 drops of copper chloride & observe. Pour the contents of the tube into the waste beaker; rinse the test tube.
6. ___Cu + ___HCl →______
Place a small piece of copper metal in test tube. Add 10 drops of 6MHCl & observe. Pour the contents of the tube into the waste beaker; rinse the test tube.
7. ___HCl + ___ NaOH →______
Add 10 drops of 6M HCl in test tube. Slowly add 10 drops of 6M NaOH, 1 drop at a time, & observe. Pour the contents of the tube down the sink; rinse the test tube.
8. ___Mg + ___O2→______
Hold a small piece of magnesium ribbon with a pair of tongs, bring over a Bunsen burner flame to observe.
Post-Lab Practice
Classify the reaction according to the type it is. Put that answer in the blank on the left. Then add coefficients to balance the reaction when necessary.
______Zn + __ H2SO4 → __ ZnSO4 + __ H2
______H2CO3 → __ CO2 + __ H2O
______CaCO3 + ___ HCl → ___ CaCl2 + ___ H2CO3
______AgNO3 + ___ Zn → ___ Zn (NO3)2 + __ Ag
______C3H8 + ___ O2 → ___ CO2 + ___ H2O
______C2H5OH + ____ O2 -→ ____ CO2 + ___ H2O
Write a balanced equation for each of the following reactions:
The reaction between potassium hydroxide and hydrofluoric acid produced potassium fluoride and dihydrogen monoxide.
Zinc metal and iron (III) oxide react to form iron and zinc (II) oxide.
Magnesium chloride is the product of a reaction between magnesium and chlorine.
Copper (II) hydroxide and potassium sulfate are produced when potassium hydroxide reacts with copper (II) sulfate.