NEET Previous Year Questions: Some Basic Concepts Of Chemistry
20 Questions MCQ Test Chemistry Class 11 | NEET Previous Year Questions: Some Basic Concepts Of Chemistry
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20 ml of decinormal solution of NaOH neutralises 25 ml of a solution of dibasic acid containing 3g. of the acid per 500 ml. The Molecular weight of the acid is
NaOH = dibasic acid
In a compound C, H and N are present in the ratio 9: 1: 3.5 by weight. Molecular mass of the compound is 108. Molecular formula of the compound is:
C% = 9/12 = 0.75 = 0.75/0.25 = 3
H% 1/1 =1 = 1/0.25 = 4
N= 3.5/14 = 0.25 = 0.25/0.25 = 1
Empirical formula = C3H4N
36+4+14=54
n = 108/54 = 2
(C3H4N) × 2
= C6H8N2
Number of atoms is 560 g of Fe (atomic mass = 56 g mol-1)
Fe atom= 560/56 =10 mole
= 10 x NA atom
option(A) = 5 mol
5 x NA
option (B) = 20/1 = 20
20 x NA
What volume of hydrogen gas at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by hydrogen?
BCl3 + 3H ⇋ B+3HCl
BCl3 + 3/2 → B + 3HCl
3/2 mol → 1 mol
1 mol B → 3/2 molH2
2 mole → 3/2 x 2 = 6/2 = 3 mole
1 mole = 22.4 liter S.T.P
3----?
= 22.4 x 3
=67.2 litre
One mole of magnesium nitride on reaction with an excess of water gives
Mg3N2 + 6H2O→ 3Mg(OH) 2 + 2NH3
How many moles of magnesium phosphate, Mg3 (PO4)2 will contain 0.25 mole of oxygen atoms?
Mg3(P04)2 → 3Mg
→2 P
→ 8 mole oxygen
8 mole of oxygen - 1 mole Mg3 (P0)2
0.25 - ? 0.25/8 = 3 x 10-2
In the reaction, 2Al (s) + 6HCl (aq) → 2Al3+ (aq) + 6Cl- (aq) + 3H2(g)
2AI + 6HCl → 2A l3+ + 6Cl- + 3H2
6 ----- 3 mol
1 mol ---- ?
3/6 = 1/2
= 0.5
At S.T.P= 22.4 - 1 mol
11.2 L
Volume occupied by one molecule of water (density = 1 g cm-3) is
Answer:
Given
Density of water (ρ) = 1g/cm3
Molar mass of water (M) = 18 g/mol
∴ Molar volume (Vm) = M/ρ
Vm = 18 cm3/mol
∴ Volume of 1 molecule of water = Vm/NA
Where NA is Avogadro number
Volume of 1 molecule of water = 18/(6.022 × 1023)
Volume of 1 molecule of water = 2.989 × 10-23 ≈ 3 × 10-23.
How many moles of lead (II) chloride will be formed from a reaction between 6.5 g of Pbo and 3.2 g of HCl?
PbO + 2HCl
6.5\223
= 2.9 x 10-2
= 2.9x10-2 - x
nx = 9a
PbCl2 + H2O
3.2/36.5
= 8.76 x 10-2
8.76 x 10-2 - x
x = 2.9 x 10-2
100 ml of PH3 on heating forms P and H2. The volume change in the reaction is
PH3 ⇋ P5 + 3/2 H2
1 mol 1+ 3/2 =2.5 mol
⟹ 100ml - 3/2 = 150ml
⟹150 - 100 = 50ml
Excess of carbon dioxide is passed through 50 mL of 0.5 M calcium hydroxide solution. After the composition of the reaction, the solution was evaporated to dryness. The solid calcium carbonate was completely neutralized with 0.1 N hydrochloric acid. The volume of the hydrochloric acid required is___________
N1V1 = N2V2
50 x 01 = 0.1 x Vml
Vm = 500ml
25.3 g of sodium carbonate, Na2CO3 is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ions, Na+ and carbonate ions, 
are respectively. (At. mass of carbon = 40)
= 2.53/106 2.59 × 10-2 5.9 × 10-2
0.238 × 0.25 = 1.18 × 10-3
250 ml - 0.238
= 0.955
0.955 
0.955
The number of atoms in 0.1 mol of a triatomic gas is
Number of atoms = number of moles x NA x atomicity
= 0.1 x 6.02 x 1023 x 3
= 1.806 x 1023
How much time (in hours) would it take to distribute one Avogadro number of wheat grains if 1020 grains are distributed each second?
6 x 1023 gram wheat
1 sec → 102O gm distributed
1 hour - 3600sec - 1020 x 3600
= 3.6 x 1023 wheat
3.6 x 1023g — 1 hour
For a reaction A + 2B → C, the amount of C formed by starting the reaction with 5 moles of A and 8 moles of B is
A +2B → C
t = 0 5 8 0
t= ? 5x 8-2x x
nx = 9a
x = 4
mole of C = 4 mole
A mixture of CaCl2 and NaCl weighing 4.44 g is treated with sodium carbonate solution to precipitate all the Ca2+ ions as calcium carbonate. The CaCO3 so obtained is heated strongly to get 0.56 g of CaO. The percentage of NaCl in the mixture is
CaCl2 + NaCl + NaC03 → CaC03
4.44 3.44
Co.C03milli = CaCO3milli
x = 3.44
%purity= 3.44/4.44 x 100
=75%
If 1 mL of water contains 20 drops, then number of molecules in a drop of water is
1/18 = 5.5 x 10-2(mole of H20
20 drops - 5.5 x 10-2 mole
= 2.77 x 10-3 x 6.023 x 1023
= 0.0167 x 1023
1.67 x 1021
In an experiment, 4 g of M2Ox oxide was reduced to 2.8g of the metal.Tf the atomic mass of the metal is 56 g mol-1, the number of O atoms in the oxide is
M20x → m
W1/E1 = W2/E2
⟹ 4E = 2.8E + 22.4
1.2E = 22.4
E= 22.4/1.2 = 18.6
Eq = mw/VF = 18.6= 56/VF
M203 VF=3
The number of O atoms is 3
Which has the maximum number of molecules among the following?
1) 44/44 = 1 mole C02
2) 48/48 =1 mole
3) 8/2 = 4 mole H2
4) 64/64 =1 mole
The density of a solution prepared by dissolving 120 g of urea in 1000 g of water is 1.15 g/ml. The molarity of this solution is:
Mass of solute taken = 120g
Molecular mass of solute = 60u
Mass of solvent = 1000g
Density of solution = 1.15g/mL
Total mass of solution = 1000 + 120 = 1120g
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