NEET Chemistry Redox Reactions Questions Solved


5mL of NHCl, 20 mL of N/2 H2SO4 and 30mL of N/3 HNO3 are mixed together and volume made one litre. The normality of the resulting solution is:

(a) N/5

(b) N/10

(c) N/20

(d) N/40

(d) M eq. of HCl = 5 x1 =5;

M eq. of H2SO4 = 20 x (1/2) = 10;

M eq.of HNO3 = 30 x (1/3) =10;

Thus, total M eq. of acid = 5+10+10=25

Total volume = 1000mL

Also M eq. = N x V,

N = 25/1000=1/40

Difficulty Level:

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When a metal is burnt, its mass is increased by 24 percent. The equivalent mass of the metal will be:

(a) 25

(b) 24

(c) 33.3

(d) 76

(c) Equivalent of metal = Equivalent of oxide 

100/E = 24/8

E = 33.3

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1g of pure calcium carbonate was found to require 50 mL of dilute HCl for complete reactions. The strength of the HCl solution is given by:

(a) 4N

(b) 2N

(c) 0.4N

(d) 0.2N

(c) M eq. of HCl = M eq. of CaCO3;

therefore N x 50 = 1/50*1000 or N = 0.4

Difficulty Level:

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The equivalent mass of H3PO4 in the following reaction is,

H3PO+ Ca(OH)2 CaHPO4 + 2H2O

(a) 98

(b) 49

(c) 32.66

(d) 40

(b) Equivalent  mass = molar mass / basicity 

M/2=98/2=49;

Basicity =2; Only two H are replaced

Difficulty Level:

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1.520g of the hydroxide of a metal on ignition gave 0.995 g of oxide. The equivalent mass of metal is:

(a) 1.520

(b) 0.995

(c) 19.00

(d) 9.00

(d) M eq. of oxide = M eq. of hydroxide;

Thus, 0.995/E+8 = 1.520/E+17

E = 9

Difficulty Level:

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0.5 g of fuming H2SO4 (oleum) is diluted  with water. This solution is completely neutralised by 26.7 mL of 0.4 N NaOH. The percentage of free SO3 in the sample is:

(a) 30.6% 

(b) 40.6%

(c) 20.6%

(d) 50%

(c) Meq. of H2SO4 + Meq.Of SO3 = Meq. of NaOH

(0.5-a)/49*1000 +a/40*1000 = 26.7 x 0.4

a = 0.103

% of SO3 = 0.103/0.5*100 = 20.6%

Difficulty Level:

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One g of a mixture of Na2CO3 and NaHCO3 consumes y equivalent of HCl for complete neutralisation. One g of the mixture is strongly heated, then cooled and the residue treated with HCl. How many equivalent of HCl would be required for complete neutralisation?

(a) 2y equivalent

(b) y equivalent

(c)  3y/4 equivalent

(d) 3y/2 equivalent

(b) 2NaHCO3 Na2CO3 +H2O + CO2

Na2CO3 Na2CO3 

The no. of equivalent of NaHCO3 = No. of equivalent of NaHCO3 formed. Thus, same equivalent of HCl will be used.

Difficulty Level:

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The chloride of a metal contains 71% chlorine by mass and the vapour density of it is 50. The atomic mass of the metal will be:

(a) 29

(b) 58

(c) 35.5

(d) 71

(a) Molar mass of metal chloride = 50x2=100;

Let metal chloride be MCln then 

Equivalent of metal = Equivalent of chloride, or 29/E = 71/35.5

E=29/2

Now a+35.5n =100

or n.E+35.5n = 100

n=2

therefore a = 2 x E= 2x(29/2) = 29.3

Difficulty Level:

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The equivalent mass of Zn(OH)2 in the following reaction is equal to its,

Zn(OH)2 + HNO3 Zn(OH)(NO3) + H2O :

(a) Formula mass/1

(b) Formula mass/2

(c) 2 x formula mass

(d) 3 x formula mass

(a) Equivalent mass Zn(OH)2 = molar mass/acidity = M/1

Acidity of Zn(OH)2 = 1; only one OH is replaced.

Difficulty Level:

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What will be the normality of a solution obtained by mixing 0.45 N and 0.60 N NaOH in the ratio 2:1 by volume?

(a) 0.4 N

(b) 0.5 N

(c) 1.05 N

(d) 0.15 N

(b) M eq.Of NaOH = 0.45 x 2V + 0.6xV

Total volume = 3V

N x 3V = 0.45 x 2V + 0.6V

N = 0.5

Difficulty Level:

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