1
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 9th January Morning Slot

A solution of sodium sulphate contains 92 g of Na+ ions per kilogram of water. The molality of Na+ ions in that solution in mol kg$$-$$1 is :
A
12
B
4
C
8
D
16

Explanation

Molality of Na+ = $${{Moles\,\,of\,\,N{a^ + }} \over {mass\,\,of\,\,{H_2}O\,\,in\,\,kg}}$$

Moles of Na+ = $${{92} \over {23}}$$ = 4

Mass of H2O = 1 kg

$$ \therefore $$   Molality = $${4 \over 1}$$ = 4
2
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 9th January Evening Slot

For the following reaction, in the mass of water produced from 445 g of C57H110O6 is :

2C57H110O6(s) + 163 O2(g) $$ \to $$ 114 CO2(g) + 110 H2O(l)
A
490 g
B
445 g
C
495 g
D
890 g

Explanation

moles of C57H110O6(s) = $${{445} \over {890}}$$ = 0.5 moles

2C57H110O6(s) + 163 O2(g) $$ \to $$ 114 CO2(g) + 110 H2O(l)

nH2O = $${{110} \over 4}$$ = $${{55} \over 2}$$

mH2O = $${{55} \over 2}$$ $$ \times $$ 18

= 495 gm
3
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 10th January Evening Slot

In the reaction of oxalate with permanganate in acidic medium, the number of electrons involved in producing one molecule of CO2 is :
A
10
B
2
C
1
D
5

Explanation

$$2\mathop M\limits^{ + 7} n{O_4} + 5{C_2}O_{_4}^{2 - } + 16{H^ + }\,\,\mathrel{\mathop{\kern0pt\longrightarrow} \limits_\,} \,2\mathop M\limits^{ + 2} {n^{2 + }}$$

                                        $$ + 10C{O_2} + 8{H_2}O$$

10 e$$-$$ trans for 10 molecules of CO2 so per molecule of CO2 transfer of e$$-$$ is '1'
4
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 11th January Morning Slot

An organic compound is estimated through Duma's method and was found to evolve 6 moles of CO2. 4 moles of H2O and 1 mole of nitrogen gas. The formula of the compound is :
A
C6H8N
B
C6H8N2
C
C12H8N
D
C12H8N2

Explanation

Molar ratio of C : H : N : : 6 : 8 : 2 i.e., 3 : 4 : 1

Thus, the correct formula is C6H8N2. .

Questions Asked from Some Basic Concepts of Chemistry

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