Download worksheet on chemical reactions

WORKSHEET ON CHEMICAL REACTIONS
Numerical Problems
1. What type of reactions are represented by the following general equations:
a) A + B  AB
b) AL + X  AX + L
c) n(X)  (X)n
d) AB + CD  AD + CB
e) C  A + B
2. What type of reactions are represented by the following reactions?
a) CaCO3  CaO + CO2
b) NH3 + HCI  NH4CI
c) Zn + H2SO4  ZnSO4 + H2
d) 2H2 + O2  2H2O
e) AgNO3 + NaCl  AgCl(s) + NaNO3
f) 2HgO  2Hg + O2
g) NH4CNO  (NH2)2CO
h) Fe + CuSO4  FeS04 + Cu
i) 3C2H2  C6H6
j) Cl2 + NaBr  2NaCI + Br2
k) CaO + H2O  Ca(OH)2 + Heat
l) Mg(OH)2  MgO + H2O
m) Cu + AgNO3  Cu(N03)2 + 2Ag
n) NH4NO2  N2 + 2H2O
3. Calculate the number of atoms in the following:
a) 0.2 moles of nitrogen molecules.
b) 3.2 g of sulphur.
4. Calculate the number of molecules in each of the following:
a) 14 g of nitrogen molecules.
5. How many atoms of oxygen are present in 300g of CaCO3? [Atomic Masses: Ca =
40, C = 12, O = 16]
6. Calculate mass of the following:
a) one atom of Calcium
b) one molecule of SO2 (Sulphur Dioxide)
7. 6.02 x 1020 molecules of a substance weigh 44mg. What is the molecular mass of the
substance?
8. The mass of a single atom of ‘X’ is 3.05 x 10-22g. Compute its Gram Atomic Mass.
9. A vessel contains 5.6g of Nitrogen (N2) gas. Calculate the following quantities:
a) Number of moles of N2
b) Number of N2 Molecules
c) Number of N atoms
10. Calculate the amount in each of the following:
a) 6g of Carbon
b) 9.9g of H2O
c) 100g of Phosphorus
[Atomic Mass: C = 12, H = 1, O=16, S = 32, P = 31]
11. 16HCl + 2KMnO4  2MnCl2 + 2KCl + 4H2O + 5Cl2
How many moles of Chlorine Gas will be produced from 3.2 moles of HCl?
12. Compute the mass of oxygen needed for the complete combustion of 114g of octane
[C8H18].
2C8H18 + 25O2  16CO2 + 18H2O
[Atomic Masses: C = 12, H = 1, O = 16]
13. How many grams of Oxygen are required to burn 40g of sulphur?
S + O2  SO2
[Atomic Masses: S = 32, O = 16]
14. Compute the mass of potassium chlorate (KClO3) that should decompose to produce
8g of oxygen.
2KClO3  2KCl + 3O2
[Atomic Masses: K = 39.1, Cl = 35.5, O = 16]
15. 0.6 moles of Cu2S is roasted in excess of oxygen to yield ‘Cu’ and ‘SO2’:
Cu2S + O2  2Cu + SO2
Calculate the mass of ‘Cu’ formed.
[Atomic Masses: Cu = 29, S =32]
16. 2.746g of a compound gave an analysis 1.95g of silver, 0.268g of sulphur and 0.538g
of oxygen. Find the empirical formula of the compound.
17. A compound on analysis gave the following composition:
Na = 32.4%, S = 22.5%, O = 45.1%
The molecular mass of the compound was found to be 142. Calculate its molecular
formula.
[Atomic Masses: Na = 23, S = 32, O = 16]
18. A compound on analysis gave the following composition:
Na = 14.31%, S = 9.97%, H = 6.22%, O = 69.5%
Molecular mass of the compound is found out to be 322. Calculate its molecular
formula.
19. Calculate empirical formula of Magnesium oxide from the following data:
0.2g of MgO was obtained by burning 0.12g of Mg in excess of Oxygen.
[Atomic Masses: Mg = 29, O = 16]
Answers to numerical problems
1.
a)
b)
c)
d)
e)
Combination reaction
Single displacement reaction
Polymerization reaction
Double displacement reaction
Decomposition reaction
2.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
Thermal decomposition reaction
Combination reaction
Single displacement reaction
Combination reaction
Double displacement reaction
Decomposition reaction
Isomerization reaction
Single displacement reaction
Polymerization reaction
Single displacement reaction
Exothermic reaction
Endothermic reaction
Single displacement reaction
Decomposition reaction
3.
a) 2.4092 x 1023 atoms
b) 6.023 x 1023 atoms
4.
a) 3.0115 x 1023 molecules
5. 5.4207 x 1024 atoms
6.
a) 6.641 x 10-23 atoms
b) 1.063 x 10-22 molecules
7. 44.021912 g
8. 183.7 g
9.
a) 0.2 moles
b) 1.2046 x 1023 molecules
c) 2.4092 x 1023 atoms of N
10.
a) 3.0115 x 1023 atoms
b) 3.313 x 1023 molecules
c) 1.943 x 1024 atoms of P
11. 1 mole
12. 400 g
13. 40 g
14. 20.433 g
15. 34.8 g
16. Ag2SO4
17. Na2SO4
18. Na2SH20O14
19. MgO
Other questions
Short answer-type questions
1. What distinguishes a physical change from a chemical change?
2. Which of the following are physical and which are chemical:
a) Disappearance of moth balls
b) Heating of iron
c) Condensation of water vapour
d) Rusting of iron
e) Digestion of food
f) Heating of iron and sulphur
3. Define the term ‘chemical reaction'. Explain it with an example.
4. What is decomposition reaction? Give one example.
5. Give one example of each:
a) a single displacement reaction.
b) a double displacement reaction.
c) a combination reaction.
d) a polymerization reaction.
6. What is a redox reaction?
7. State the electronic concept of oxidation and reduction.
8. Translate the following statements into chemical equations and balance:
a) Aluminium metal replaces iron from ferric oxide (Fe2O3) giving aluminium oxide
and iron.
b) Phosphorous burns in oxygen to form phosphorous pentoxide.
c) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
d) Hydrogen sulphide burns in air to give water and sulphur dioxide.
e) Calcium oxide reacts with water to give calcium hydroxide.
f) Magnesium nitride reacts with water to give magnesium hydroxide and ammonia.
g) Barium chloride reacts with sodium sulphate to give barium sulphate and sodium
chloride.
9. For each of the following reactions mention which is being oxidised or reduced:
a) CuO + H2O  Cu + H2O
b) H2 + CI2  2HCl
c) SO2 + 2H2S  2H20 + 3S
d) Cl2 + 2KI  2KCl + I2
e) Zn + H2SO4  ZnS04 + 4H2O
f) PbS + 4H2O2  PbS04 + 4H2O
g) 2NaCl + H2SO4  Na2SO4 + HCl
h) CU2+ + H2  Cu + 2H+
10. The chemical formula of ammonia is NH3. What information does this convey?
11. Define rate of reaction. Give one example each of slow and fast reactions.
12. Balance the following equations:
a) NaHCO3  Na2CO3 + H2O + CO2
b) K2Cr207 + KOH  H2O + K2Cr04
c) Mg + H2SO4  MgSO4 + H2
d) Ar2O3 + H2S  Ar2S + H2O
e) C2H6 +702  O2 + H2O
f) KI + H2O2  KOH +I2
g) FeSO4 + H2SO4 + Cl2  Fe2(SO4)3 + HCl
h) S + HNO3  H2SO4 + NO2 + H2O
i) KMnO4 + H2SO4  K2SO4 + MnSO4 + H2O + Na2SO4
13. From the following identify the redox reactions, oxidizing and reducing agent:
a) Ca(S) + Cl2(g)  CaCl2
b) CuSO4 + Fe  FeSO4 + Cu
c) CuO + H2  Cu + H2O
d) KOH + HI  KI + H2O
e) Zn + H2SO4  ZnSO4 + H2
f) 2Na + Cl2  NaCl
g) Ca + Cl2  CaCl2
h) H2S + Cl2  2HCl + S
i) Cu2+ + Zn  Zn2+ + Cu