CLICK HERE FOR CHEMICAL REACTIONS AND EQUATIONS WORKSHEET 3
61. A balanced chemical equation has equal masses of various elements in ___________ and ___________ .
Answer/Explanation
Answer:
Explanation: reactants, products
62.
is an example of ___________ reaction.
Answer/Explanation
Answer:
Explanation: decomposition
63. All combustion reactions are oxidation reactions. [True/False]
Answer/Explanation
Answer:
Explanation: True
64. Displacement reaction can be redox reaction also. [True/False]
Answer/Explanation
Answer:
Explanation: True
65. In H2S + Cl2 → 2HCl + S, Cl2 is oxidising agent and H2S is reducing agent. [True/False]
Answer/Explanation
Answer:
Explanation: True
66. CaO + 2HCl → CaCl2 + H2O is neutralisation reaction. [True/False]
Answer/Explanation
Answer:
Explanation: True
67. Chemical reactions are those processes where new substances with old properties are formed. [True/False]
Answer/Explanation
Answer:
Explanation: False
Direction: Match Column I with Column II.
68.
Answer/Explanation
Answer:
Explanation:
(i) (C)
(ii) (D)
(iii) (A)
(iv) (B)
69. State one basic difference between a physical change and a chemical change. [CBSE 2011]
Answer/Explanation
Answer:
Explanation:
In physical change, no new substance is formed whereas in a chemical change a new substance(s) is/are formed.
70. What is meant by a chemical reaction? [CBSE 2011]
Answer/Explanation
Answer:
Explanation:
The reaction representing a chemical change is called chemical reaction.
71. On what basis is a chemical equation balanced?
Answer/Explanation
Answer:
Explanation:
It is based on law of conservation of mass.
72. Balance the given chemical equation:
Al(s) + CuCl2(ag) → AlCl(aq) + Cu(s)
Answer/Explanation
Answer:
Explanation:
2Al(s) + 3CuCl2(aq) → 2AlCl3(aq) + 3Cu(s)
73. Balance the given chemical equation:
Answer/Explanation
Answer:
Explanation:
74. Balance the given chemical equation:
Answer/Explanation
Answer:
Explanation:
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
75. AgNO3(aq) + NaCl(aq) → AgCl(g) ↓ + NaNO3(aq)
FeS + H2SO4 → FeSO4 + H2S ↑
Consider the above mentioned two chemical equations with two different kinds of arrows ( ↑ and ↓) along with product. What do these two different arrows indicate? [CBSE 2011]
Answer/Explanation
Answer:
Explanation:
↑ shows the gas evolved whereas ↓ shows insoluble substance (precipitate) formed.
76. Hydrogen being a highly inflammable gas and oxygen being a supporter of combustion, yet water which is a compound made up of hydrogen and oxygen is used to extinguish fire. Why? [CBSE 2011]
Answer/Explanation
Answer:
Explanation:
It is because properties of compound (H2O) are different from properties of its constituting elements i.e. H2 and O2.
77. What happens chemically when quicklime is added to water filled in a bucket?
Answer/Explanation
Answer:
Explanation:
Quicklime reacts with water to form slaked lime and produces lot of heat and hissing sound.
78. What change in colour is observed when white silver chloride is left exposed to sunlight? State the type of chemical reaction in this change.
Answer/Explanation
Answer:
Explanation:
Silver chloride becomes grey. It is a photochemical decomposition reaction.
79. How will you define a reducing agent?
Answer/Explanation
Answer:
Explanation:
Reducing agent is a substance which can lose electrons or which can add hydrogen or remove oxygen.
80. Potato chips manufacturers fill the packet of chips with nitrogen gas. Why? [DoE]
Answer/Explanation
Answer:
Explanation:
To provide an inert atmosphere to prevent chips from getting oxidised. N2 does not allow chips to get spoiled by oxidation.
81. Why do gold and platinum not corrode in moist air?
Answer/Explanation
Answer:
Explanation:
They are least reactive and do not react with substances present in moist air.
82. Write two characteristics associated with rancid food.
Answer/Explanation
Answer:
Explanation:
Unpleasant smell and unpleasant taste.
83. How will you indicate the following effect in a chemical equation? A solution made in water.
Answer/Explanation
Answer:
Explanation:
A solution made in water is indicated by writing symbol (aq) with the symbol or formula of the substance concerned, aq stands for aqueous.
84. Give reason for the following:
The burning of natural gas is an exothermic reaction.
Answer/Explanation
Answer:
Explanation:
Burning of natural gas is an exothermic reaction because heat is produced in this reaction.
85. Give one example of a redox reaction which is also a combination reaction.
Answer/Explanation
Answer:
Explanation:
2Mg + O2 → 2MgO
86. Balance the given chemical equation:
HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O
Answer/Explanation
Answer:
Explanation:
2HNO3(aq) + Ca(OH)2(aq) > Ca(N03)2(^) + 2H2O(l)
Fill in the Blanks
1. The addition of oxygen to a substance is called …………. whereas removal of oxygen is called …………. .
2. The addition of hydrogen to a substance is called …………. whereas removal of hydrogen is called …………. .
3. Precipitation reactions produce insoluble …………. .
4. Reactions in which energy is given out are known as …………. .
5. Reaction in which an element displaces another element from its compound is called …………. .
6. Two antioxidants which are usually added to fat and oil containing foods to prevent rancidity, are …………., …………. .
7 …………. is the process in which metals are eaten up gradually by the action of air, moisture or a chemical on
their surface.
8. 2 FeSO4 → Fe2O3 + SO2 + ………….
9. Na2SO4 + BaCl2 → …………. + 2NaCl
10. Complete the missing components/variables given as x and y in the following reactions:
(a) Pb (NO3)2 (aq) + 2KI (aq) → Pbl2 (x) + 2KNO3 (y)
(b) Cu (s) + 2AgNO3 (aq) → Cu (NO3)2 (aq) + x (s)
Answers
1. oxidation, reduction
2. reduction, oxidation
3. salts
4. exothermic reactions
5. displacement reaction
6. BHA and BHT
7. Corrosion
8. SO3
9. BaSO4
10. (a) x → (s); y → (aq);
(b) x → 2Ag