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Some Basic Concepts of Chemistry · Question 17

JEE Main 2026 (Online) 21st January Morning ShiftMCQMedium📈 Topic in 42% papers+4−1
1

80 mL of a hydrocarbon on mixing with 264 mL of oxygen in a closed U-tube undergoes complete combustion. The residual gases after cooling to 273 K occupy 224 mL. When the system is treated with KOH solution, the volume decreases to 64 mL. The formula of the hydrocarbon is :

  1. C2H2
  2. C2H4
  3. C4H10
  4. C2H6

Answer

(1) C2H2

Solution

CxHy + (x + y4 )O2 xCO2 + y2H2O(l)

Gas left after KOH treatment = unused O2 = 64 mL

Volume of CO2 (absorbed by KOH) = 224 − 64 = 160 mL

80x = 160 x = 2

O2 used = 264 − 64 = 200 mL

80 (x + y4 ) = 200 x + y4 = 2.5 y = 2

Hydrocarbon = C2H2

Answer: (1)

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2

Aqueous HCl reacts with MnO2(s) to form MnCl2(aq), Cl2(g), and H2O(l). What is the weight (in g) of Cl2 liberated when 8.7 g of MnO2(s) is reacted with excess aqueous HCl solution? (Given Molar mass in g mol-1 Mn = 55, Cl = 35.5, O = 16, H = 1)

  1. 14.2
  2. 21.3
  3. 7.1
  4. 71
JEE Main 2026 (Online) 21st January Evening Shift
3

20 mL of sodium iodide solution gave 4.74 g silver iodide when treated with excess of silver nitrate solution. The molarity of the sodium iodide solution is M. (Nearest Integer value) (Given : Na = 23, I = 127, Ag = 108, N = 14, O = 16 g mol-1)

JEE Main 2025 (Online) 8th April Evening Shift
4

Thyroxine, the hormone, has the structure given below [figure] The percentage of iodine in thyroxine is %. (nearest integer) (Given molar mass in g mol-1 C : 12, H : 1, O : 16, N : 14, I : 127)

JEE Main 2025 (Online) 7th April Morning Shift
5

Butane reacts with oxygen to produce carbon dioxide and water following the equation given below. C4H10(g) + 132O2(g) 4CO2(g) + 5H2O(l) If 174.0 kg of butane is mixed with 320.0 kg of O2, the volume of water formed in liters is . (Nearest integer) [Given : (a) Molar mass of C, H, O are 12, 1, 16 g mol-1 respectively, (b) Density of water = 1 g mL-1]

JEE Main 2025 (Online) 7th April Evening Shift
6

Fortification of food with iron is done using FeSO4 7H2O. The mass in grams of the FeSO4 7H2O required to achieve 12 ppm of iron in 150 kg of wheat is (Nearest integer) [Given: Molar mass of Fe, S and O respectively are 56, 32 and 16 g mol-1]

JEE Main 2025 (Online) 4th April Morning Shift
7

The amount of calcium oxide produced on heating 150 kg limestone (75% pure) is kg. (Nearest integer) Given: Molar mass (in g mol-1) of Ca-40, O-16, C-12

JEE Main 2025 (Online) 4th April Evening Shift
8

Among 10-9 g (each) of the following elements, which one will have the highest number of atoms? Element: Pb, Po, Pr and Pt

  1. Pr
  2. Pt
  3. Po
  4. Pb
JEE Main 2025 (Online) 3rd April Morning Shift
9

Mass of magnesium required to produce 220 mL of hydrogen gas at STP on reaction with excess of dil. HCl is Given: Molar mass of Mg is 24 g mol-1.

  1. 0.24 mg
  2. 235.7 g
  3. 2.444 g
  4. 236 mg
JEE Main 2025 (Online) 3rd April Evening Shift
10

10 mL of 2 M NaOH solution is added to 20 mL of 1 M HCl solution kept in a beaker. Now, 10 mL of this mixture is poured into a volumetric flask of 100 mL containing 2 moles of HCl and made the volume up to the mark with distilled water. The solution in this flask is :

  1. 0.2 M NaCl solution
  2. 20 M HCl solution
  3. Neutral solution
  4. 10 M HCl solution
JEE Main 2025 (Online) 3rd April Evening Shift
11

X g of nitrobenzene on nitration gave 4.2 g of m-dinitrobenzene. X = g. (nearest integer) [Given : molar mass (in g mol-1) C : 12, H : 1, O : 16, N : 14]

JEE Main 2025 (Online) 3rd April Evening Shift

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