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Very short answer questions
(V.S.A) : X Chemical reactions and
Chemical Equation:FA
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1.
Arrange the following metals in the decreasing under of reactivity or electro
positive character.
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K Zn
Na Fe Pb Cu
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2.
Which of them will be a reducing agent a metal or non metal?
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3.
Balance the chemical equation
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4.
Select the combination reaction from following
(i)KClO3
® KCl + 3 O2
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5.
Select the decomposition reaction from following
(i)
2H2O + O2 ® 2H2 O
(ii)
CaCO3 ------Heat------® CaO + CO2
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6.
Select the double displacement reaction
(i)
BaCl2 + H2SO4 ---® Ba SO4 + H2
(ii)
2KBv + Cl2 ® K Cl2 + Bv2
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7.
Fill in the following about reactivity series of metal
(a)
the …………………. Metal replaces the ………………. Metal from its salt solution.
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8.
Which of the following is not the necessary condition for rusting
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(i)
Presence of oxygen (ii) Presence of catalyst (iii) Presence of moisture
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9.
Which of the following is required for prevention of corrosion?
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(i)
coating of less electropositive metal
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(ii)
coating of move electropositive metal
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10.
Choose the correct about rancidity
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(i)
Rancidity is a reduction process (ii) Rancidity is an oxidation
process
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Answers
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1. K
> Na > Zn > Fe > Pb > Cu
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2. Non
metal
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3. 2
Na(s) +2 H2O ® 2NaOH
+ 2H2
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4. S +
O2 ® SO2
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5.
CaCO3 ------Heat® CaO + CO2
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6.
BaCl2 + H2SO4 ® Ba SO4 + H2
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7.
Strong, Weak
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8.
Presence of catalyst
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9.
Coating with move electropositive metal
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10.
Rancidity is an oxidation process
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See some
questions: Short Answer type Question (2 marks)
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1.
(i) What happens when aqueous solution of barium chloride is added to aqueous
sodium sulphate solution?
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(ii)
When silver coloured metal (A) is added to dilute sulphuric acid, solution
(B) is formed which is colourless solution and a gas (c) is evolved which is
colourless name ‘A’, ‘B’ and ‘C’ and write the equation?
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(iii)
An ‘A’ blue coloured crystalline salt on heating decomposes to ‘B’ white
substance. W hen in
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blue
salt solution, a metal (Zinc) is added, its gives rise to colourless solution
‘C’ wth leaving behind ‘D’ reddish brown metal.
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2.
Name the compounds ‘A’, ‘B’, ‘C’ and ‘D’
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(iv)
A reaction mixture of chromium Oxide is heated with aluminum powder on
strong heating
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3.
a. Write the reaction?
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b.
Give one application of this reaction?
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(v)
Define Rusting?
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4.
Give two methods of protection of metal trans rusting.
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5.
(i) Rusting is a slow electrochemical process in which hydrated oxide of
metal in formed from metal when it comes in with air moisture (ii) By
Painting, by galvanization, by tinning
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6.
(i) Explains the term ‘corrosion’?
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(ii)
Write the chemical reaction of corrosion of Iron?
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(iii)
Name two metals which corrodes easily?
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(iv)
Aluminum corrodes in moist air but is widely used is making utensils.
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(v)
what is galvanization and why do we use Zn for it?\
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7.
(i) What is rancidity? Where does it happen
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(ii)
what are anti oxidants? Why are they added fat and oil containing food to
prevent from rancidity?
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(iii)
why do most items puffed with nitrogen.
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Solution:
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1.
White precipitate of BaSO4 is obtained. Reaction will be as
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Na2SO4 +
BACl2 ----------------® BaSO4 + 2NaCl
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2. A
is Zinc, B is ZnSO4 solutions C is H2gas and reactions will be
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Zn (s)
+ H2SO4 (d) ------------® Zn SO4 (aq) + H2 (g)
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3. A,
B, C, and D are respectively-
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CuSO4,
5 H2O, CuSO4, ZnSO4 (aq), Cu (s)
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4.
(i)Cr2O3 + 2Al ------® Al2O3 + 2 Cr
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(ii)
This reaction is used in termite welding
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5. (i)
The process of slow destruction of metals when exposed to air, moisture and
pollutant gases , in called as corrasim
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(ii)
Fe + 3H2 + 2H2O
------------® Fe2O3 x H2O
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(iii)
Formation of green coating on copper and formation of thin layer of oxide on
aluminum are example of corrosion.
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(iv)
Aluminum forms oxide layer on exposure to air, this oxide layer further
checks corrosion.
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(v)
Galvanization is a process in which Zinc layer is applied on Iron. It is used
to protect iron from rusting.
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6. (i)
The oxidative deterioration of oils and fats leading to stinking smell or
stale taste is known as rancidity.
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(ii)
Anti Oxidants are those chemicals which an addition to fat and oil checks it
from rancidityan addition of anti oxidants fatty food is protected from stale.
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(iii)
Nitrogen is filled in potato chips & other food to create anaerobic (air
free atmosphere) which avoids rancidity.
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Class 09 Atoms and Molecules Numerical Problem based on Law of chemical Combination Law of conservation of mass Law of constant proportion Empirical formula 1. If 10 grams of CaCO 3 on heating gave 4.4g of CO 2 and 5.6g of CaO, show that these observations are in agreement with the law of conservation of mass.(Based on Law of conservation of mass) Solution: Mass of the reactants = 10g ; Mass of the products = 4.4 + 6.6g = 10g Since the mass of the reactants is equal to the mass of the products, the observations are in agreement with the law of conservation of mass. 2. 1.375 g of cupric oxide was reduced by heating and the weight of copper that remained was 1.098g. In another experiment 1.179 g of copper was dissolved in nitric acid and the resulting copper nitrate was converted into cupric oxide by ignition . The weight of cupric oxide formed was 1.476 g. which law of chemical combinations does this data state? Solution: in first experiment: Copper oxide = 1....
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