CBSE Class 10 Chemistry Chemical Reaction and Equations Worksheet Set C

Question. A substance which oxidizes itself and reduces other is known as:
(a) Oxidising agent
(b) Reducing agent
(c) Both (a) and (b)
(d) None of these.

Answer: B

Question. The reaction between lead nitrate and potassium iodide present in aqueous solution is an example of
(a) Decomposition Reaction
(b) Displacement Reaction
(c) Double Displacement Reaction
(d) Neutralisation Reaction

Answer: C

Question. In an electric cell where electrolysis is carried out, anode has:
(a) Positive charge
(b) Negative charge
(c) Connected to negative terminal of the battery
(d) None of these is correct

Answer: A

Question. Which of the following is not a balanced equation?
(a) Fe + Cl₂ →FeCl₃
(b) Mg + CuSO₄→ MgSO4 +Cu
(c) NaOH + HCl → NaCl + H₂O
(d) Zn + S →ZnS

Answer: A

Question. Dissolving sugar is an example of:
(a) Physical change
(b) Chemical change
(c) Redox reaction
(d) None of these

Answer: A

Question. What happens when dilute hydrochloric acid is added to iron filling? Tick the correct answer
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced
(c) No reaction takes place
(d) Iron salt and water are produced

Answer: A

Question. A student adds lead and silver to two different test tubes containing an equal amount of Copper Sulphate solution. The student observes that the color of the solution in the test tube with lead changes. What explains the change in the color of the solution?
(a) A displacement reaction takes place as lead replaces copper from the solution.
(b) A combination reaction takes place as lead combines with sulphate in the solution.
(c) Decomposition reaction takes place as copper dissociates from sulphate in the solution.
(d) A double displacement reaction takes place as copper dissociates from sulphate and lead combines with sulphate in the solution.

Answer: B

Question. Some crystals of copper sulphate were dissolved in water. The color of the solution obtained would be:
(a) Green
(b) Red
(c) Blue
(d) Brown

Answer: C

Question. In an electrolytic cell where electrolysis is carried, cathode has:
(a) Positive change
(b) Negative charge
(c) Connected to negative terminal of the battery
(d) None of these is correct.

Answer: A

Question. In the decomposition of lead (II) nitrate to give lead (II) oxide, nitrogen dioxide and oxygen gas, the coefficient of nitrogen dioxide (in the balanced equation) is
(a) 1
(b) 2
(c) 3
(d) 4

Answer: D

Assertion and Reason Type MCQs : 

Following questions consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
A. Both assertionand reason are true, and reason is the correct explanation of assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false and reason is true.

Question. Assertion(A): After white washing the walls, a shiny white finish on walls is obtained after three or four days.
Reason(R): Calcium hydroxide reacts with Carbon dioxide to form Calcium Carbonate which gives shiny white finish.

Answer: A

Question. Assertion(A): Iron nails turn blue colour copper sulphate solution to green colour.
Reason(R): Copper is more reactive than iron.

Answer: C

Question. Assertion(A): Acidification of water decreases its conductivity during electrolysis.
Reason(R): H⁺ ions are released which hinder the flow of charges.

Answer: D

Question. Assertion(A): The glucose combines with oxygen in the cells of our body and provides energy.
Reason(R): Respiration is an example of oxidation reaction.

Answer: B

Question. Assertion(A): Sulphur dioxide and Sulphur trioxides are released during the decomposition of iron sulphate.
Reason(R): This is an example of thermal decomposition.

Answer: B

Question. Assertion(A): In double displacement reactions, no precipitate is formed.
Reason(R): Barium Sulphate is precipitated during the double displacement reaction between Sodium Sulphate and Barium Chloride.

Answer: D

Question. Assertion(A): The number of atoms of each element remains the same, before and after a chemical reaction.
Reason(R): Any chemical equation can be unbalanced because the mass may not be same on both sides of the equation.

Answer: C

Question. Assertion(A): Oxidation and reduction take place simultaneously in a reaction.
Reason(R): All chemical reactions are redox reactions.

Answer: C

VERY SHORT ANSWER TYPE QUESTIONS:

Question. In electrolysis of water, why is the volume of gas collected over one electrode double that of the other electrode?
Answer: The amount of H is double than that of O. The two electrodes collect H2 and O2 separately, therefore, the volume of gas collected in one electrode is double the volume of gas collected in the other electrode.

Question. Name the compound used for testing CO₂ gas.
Answer: Calcium hydroxide solution (freshly prepared), also called lime water, is used to test CO₂ gas.

Question. What is a redox reaction?
Answer: A redox reaction can be defined as a chemical reaction in which electrons are transferred between two reactants participating in it.

Question. What happens when water is added to solid calcium oxide taken in a container? Write a chemical formula for the same.
Answer: When calcium oxide is added to water it forms calcium hydroxide Called slaked lime.
CaO +H₂O →Ca(OH)₂ The reaction between water and CaO is an exothermic reaction.

Question. Why is photosynthesis considered as an endothermic reaction?
Answer: Photosynthesis is considered an endothermic reaction, because during the process of photosynthesis, energy from the sun or sunlight is being absorbed.

SHORT ANSWER TYPE QUESTIONS:

Question. Why a combustion reaction an oxidation reaction?
Answer: Combustion reaction because it is always carried out in the presence of air or oxygen for e.g. CH4 (g) + 2O₂ (g) → Co₂ (g) +2H₂O (l).

Question. A student took 2-3 g of a substance X in a glass beaker & poured water over it slowly. He observed bubbles along with hissing noise. The beaker becomes quite hot. Identify X. What type of reaction is it?
Answer: X = Calcium oxide (Quick lime), Combination reaction.

Question. Why should a magnesium ribbon be cleaned before burning in air?
Answer: Magnesium ribbon is cleaned before burning to remove the protective layer of basic magnesium Oxide from the surface of magnesium ribbon.

Question. Identify the type of chemical reaction
(i) A→B+C
(ii) AB+CD→AD+CB
Answer: (i) Decomposition reaction
(ii) Double displacement reaction

Question. Why does not silver evolve hydrogen on reacting with dil. H₂SO₄?
Answer: Silver do not evolve hydrogen on reacting with dil. H₂SO₄ as silver is less reactive metal than hydrogen.

CASE STUDY BASED QUESTIONS: 

I:  Read the following and answer the questions
The double displacement reaction is a type of chemical reaction. where two compounds react and the cation and anion of the two reactants 6 places forming 2 new products. The ionic compounds considered as reactants are water soluble. One of the products is formed as a precipitate or as a gas which is water soluble.

Question. Which metallic spoon can be used to stir Lead nitrate solution ?
A. Sodium
B. Silver
C. Iron
D. Aluminum

Answer: B

Question. The reaction between lead nitrate and potassium iodide is an example of.
A. Combination reaction
B. Decomposition Reaction
C. Displacement reaction
D. Double displacement reaction.

Answer: D

Question. What was the color of the precipitate formed when Lead nitrate reacts with Potassium iodide ?
A. Blue
B. Red
C. Yellow
D. Orange

Answer: C

II. We have observed that iron articles are shiny when new, but get coated with a reddish brown powder when left for some time. This process is commonly known as rusting of iron.
Some other metals also get tarnished in this manner. Have you noticed the colour of the coating formed on copper and silver? When a metal is attacked by substances around it such as moisture, acids, etc., it is said to corrode and this process is called corrosion.

Question. If a metal under goes uniform corrosion it becomes
A. Thicker
B. Perforated
C. Thinner
D. None of the above

Answer: C

Question. The chemical formula of rust is
A. Fe₂O₃
B. Fe₃o₄
C. Fe₂O₃ XH₂O
D. Fe₃O₄. XH₂O

Answer: C

Question. Which of the following metal is highly corrosive ?
A. Zinc
B. Aluminum
C. Gold
D. Silver

Answer: B

LONG ANSWER TYPE QUESTIONS:

Question. What happens to lime water when CO₂ gas is bubbled through it in excess?
Answer: When CO₂ gas is bubbled through lime water in excess then initially it becomes milky but after some time its milkiness disappears. This is because initially calcium carbonate is formed which causes the lime water to turn milky and when further CO₂ is passed calcium bicarbonate is formed which turns the solution colorless.

Question. A student dropped few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? Write balanced chemical equation for both the change observed?
Answer: When marble (CaCO₃ )reacts with dil. HCl, CO₂ gas evolved
CaCO₃ (s) +2HCl (aq)→ CaCl₂ (aq) + H₂O (l) + CO₂ (g)
When this gas is evolved and is passed through lime water, becomes milky due to the formation of insoluble Calcium carbonate.
Ca (OH)₂ + CO₂ (g)→ CaCO₃ (s) +H₂O (l)
But when milkiness disappears i.e. when CO₂ gas is passed in excess through CaCO₃ (s) CaCO₃ (s) + CO₂ (g) +H₂O (l)→Ca (HCO₃)₂ (aq.)

Question. A compound ‘X’ is used for drinking, has pH =7. Its acidified solution undergoes decomposition in presence of electricity to produce gases ‘Y ’and ‘Z ’. The volume of Y is double than Z. Y is highly combustible whereas Z is supporter of combustion. Identify X, Y & Z and write the chemical reactions involved.
Answer: In the given situation, X= H₂O, 2Y =H₂ and Z=O₂.
The chemical reaction involved is: 2H₂O→2H₂+O₂

Question. An aqueous solution of metal nitrate P reacts with sodium bromide solution to form Yellow ppt of compound Q which is used in photography. Q on exposure to sunlight undergoes decomposition reaction to form metal present in P along with reddish brown gas. Identify P &Q. Write the chemical reaction & type of chemical reaction and define it?
Answer: P = Ag NO₃ Q= AgBr 2AgBr→ 2Ag+Br₂
Photochemical decomposition.
The decomposition reaction that occurs in the presence of light is photochemical reaction.

Question. A substance X used for coating iron articles is added to a blue solution of a reddish-brown metal Y, the colour of the solution gets discharged. Identify X and Y & also the type of reaction.
Answer: Here, a substance X used for coating iron articles is added to a blue solution of a reddish-brown metal Y , the colour of the solution gets discharged. Therefore, X is Iron ( Fe ) Y is Copper ( Cu ).
Also, it is a type of a displacement reaction.