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10th Grade > Chemistry

CHEMICAL REACTIONS AND EQUATIONS MCQs

Total Questions : 51 | Page 1 of 6 pages
Question 1. The balanced chemical equation for potassium reacting with water is:
  1.    K(s)+2H2O(l)→KOH(aq)+H2(g)
  2.    2K(s)+H2O(l)→2KOH(aq)+H2(g)
  3.    K(s)+H2O(l)→KOH(aq)+H2(g)
  4.    2K(s)+2H2O(l)→2KOH(aq)+H2(g)
 Discuss Question
Answer: Option D. -> 2K(s)+2H2O(l)→2KOH(aq)+H2(g)
:
D
Potassium reacts with water to form potassium hydroxide along with hydrogen. The chemical equation for this reactionis given below:
K(s)+H2O(l)KOH(aq)+H2(g)
We can see that:
Reactant
Product
Elements Symbol
No. of atoms
Elements Symbol
No. of atoms
K
1
K
1
H
2
H
3
O
1
O
1
Now in order to balance the equation the number of atoms on both reactants and the products side should be equal. By applying hit and trialmethod the balanced equation of the given reaction is:
2K(s)+2H2O(l)2KOH(aq)+H2(g)
Question 2. Beakers A, B, and C contain zinc sulphate, silver sulphate, and ferrous sulphate solutions respectively. Copper filings are added to each beaker. Blue colour will appear in which of the following beakers?
  1.    Beaker A
  2.    Beaker B
  3.    Beaker C
  4.    All the beakers
 Discuss Question
Answer: Option B. -> Beaker B
:
B
Copper is less reactive than zinc and iron, but is more reactive than silver. Hence, copper displaces silver from its salt solution.
Copper on reaction with silver sulphate forms copper sulphate and silver. The solution colour changes as copper sulphate is blue in colour. The reaction takes place as follows:
2AgSO4(aq)+Cu(s)2Ag(s)+CuSO4(aq)
Hence colour change will be observed in the case of beaker B.
Question 3. The conversion of CaCO3 into CaO is an example of ____________ reaction.
  1.    decomposition
  2.    combination
  3.    double displacement
  4.    displacement
 Discuss Question
Answer: Option A. -> decomposition
:
A
The conversion of calcium carbonate(CaCO)3 to calcium oxide(CaO) is an example of decomposition reaction. During the reaction, calcium carbonate decomposes on heating to form calcium oxide and carbon dioxide. The reaction takes place as follows:
CaCO3(s)HeatCaO (s)+CO2(g)
Question 4. Which of the following is a displacement reaction?
  1.    CaO(s)+H2O(l)→Ca(OH)2(aq)
  2.    MgCO3(s)→MgO(s) +CO2(g)
  3.    2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)
  4.    H2(g)+Cl2(g)→2HCl(g)
 Discuss Question
Answer: Option C. -> 2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)
:
C
The chemical reaction in which a more reactive element displaces a less reactive element from its compound is called displacement reaction.
Among the given options, the reaction between sodium and water to form sodium hydroxide and hydrogen gas is an example of a displacement reaction. This is because sodium, which is more reactive than hydrogen, displaces it from water.
Question 5. Which amongst the following can be observed when zinc granules are added to dilute hydrochloric acid taken in a test tube?
  1.    No change takes place
  2.    The colour of the solution turns yellow
  3.    A pungent smelling gas is liberated
  4.    Small bubbles are formed
 Discuss Question
Answer: Option D. -> Small bubbles are formed
:
D
When zinc granules areadded todilute hydrochloric acid taken in a test tube, the zinc metal displaces the hydrogen from the acid and hydrogen gas comes out in the form of small bubbles. This is a displacement reaction. It occurs as follows:
Zn(s)+2HCl(aq)ZnCl2(aq)+H2(g)ZincHydrochloricZincHydrogenacidchloride
Question 6. Stale food gives a bad taste and because of ______.
  1.    corrosion
  2.    rusting
  3.    tanning
  4.    rancidity
 Discuss Question
Answer: Option D. -> rancidity
:
D
When food containing fats and oils come in contact with oxygen in the air, it undergoes oxidation. This causes bad smell and change in taste of food. This process is called rancidity.
Question 7. A reddish brown gas is released on heating lead nitrate. The type of reaction involved here is:
  1.    combination reaction
  2.    displacement reaction
  3.    decomposition reaction
  4.    double displacement reaction
 Discuss Question
Answer: Option C. -> decomposition reaction
:
C
A decomposition reaction is where one reactant is broken into multiple simple products.
When lead nitrate (2Pb(NO3)2) is heated, it decomposes into lead oxide (PbO), nitrogen dioxide (NO2) and oxygen (O2). The reaction occurs as follows:
2Pb(NO3)2(s)Heat2PbO (s)+4NO2(g)+O2(g)
Thereddish brown gas released is NO2.
Question 8. When carbon dioxide gas is passed through lime water,
  1.    calcium hydroxide is formed.
  2.    white precipitate of CaO is formed.
  3.    white precipitate of CaCO3 is formed.
  4.    colour of lime water disappears.
 Discuss Question
Answer: Option C. -> white precipitate of CaCO3 is formed.
:
C
When CO2 is passed through lime water, a white precipitate of CaCO3 is formed, which turns lime water milky. The reaction occurs as follows:
Ca(OH)2(aq)+CO2(g)CaCO3(s)+H2O(l)
Question 9. Which of the following compound is obtained when quicklime reacts with water?
  1.    Ca(NO3)2
  2.    Ca(HCO3)2
  3.    Ca(OH)2
  4.    CaCO3
 Discuss Question
Answer: Option C. -> Ca(OH)2
:
C
Slaked lime (Ca(OH)2)is formed when quicklime (CaO)reacts with water. The equation of the reaction is given below:
CaO(s)+H2O(l)Ca(OH)2(aq)+Heat
This is an example of a combination reaction because there is only one product that is being formed from the reaction between the tworeactants.
Question 10. 3MnO2(s)+4Al(s)3Mn(s)+2Al2O3(s)
In the above reaction, the oxidising agent is:
  1.    MnO2
  2.    Al
  3.    Al2O3
  4.    Mn
 Discuss Question
Answer: Option A. -> MnO2
:
A
An oxidising agent is a chemical compound that undegoes reduction in a redox reaction. In the given reaction, manganese dioxide is behaving as an oxidising agent as it is getting reduced to manganese.

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