Chemistry · JEE

Mole concept, molar mass, percentage composition, empirical and molecular formulae Previous Year Questions for JEE

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Q1ChemistryUnit 1: Some Basic Concepts in Chemistry

What is the density of wet air with

75 \%

relative humidity at 1 atm and

300 \mathrm{K}

? Given : vapour pressure of

H_{2} O

is 30 torr and average molar mass of air is

29 g / m o l

Q2ChemistryUnit 1: Some Basic Concepts in Chemistry

Calculate the volume occupied by 40 g. of a

C H_{4}

\mathrm{S.T.P}

if its

\mathrm{V} . \mathrm{D}

. is 8

Q3ChemistryUnit 1: Some Basic Concepts in Chemistry

1.00 \mathrm{g}

of a hydrated salt contains

0.2014 \mathrm{g}

of iron,

0.1153 \mathrm{g}

of sulphur

0.2301 \mathrm{g}

of oxygen and 0.4532 g of water of crystallisation. If its empirical formula

(\boldsymbol{F e}=\mathbf{5 6} ; \boldsymbol{S}=\mathbf{3 2} ; \mathbf{0}=\mathbf{1 6})

F e S O_{x} \cdot y H_{z} O,

then find the value of

x, y

and

z

Q4ChemistryUnit 1: Some Basic Concepts in Chemistry

The formula that gives the symbolic representation of the actual number of atoms of various elements present in one molecule of the compound, is called:

Q5ChemistryUnit 1: Some Basic Concepts in Chemistry

A compound of sodium does not give

C O_{2}

when heated but it gives

C O_{2}

when treated with dilute acids. A crystalline compound is found to have 37.1\% Na and 14.52\%

\boldsymbol{H}_{\mathbf{2}} \boldsymbol{O}

. Hence, the compound is :

Q6ChemistryUnit 1: Some Basic Concepts in Chemistry

The composition of a sample of Wustite is

F e_{0.93}

O. What is the percentage of iron present as

F e^{3+}

in total iron?

Q7ChemistryUnit 1: Some Basic Concepts in Chemistry

A solution is prepared by adding 2 g of substance

A

to 18 g of water. The mass percent of the solute is:

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Why practise PYQs for Mole concept, molar mass, percentage composition, empirical and molecular formulae?

PYQs reveal recurring concepts, common traps, and the difficulty level JEE expects. Solving them builds exam temperament and time management.

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Our bank includes exam-style MCQs aligned with JEE Main Chemistry syllabus for Mole concept, molar mass, percentage composition, empirical and molecular formulae, covering the same topics as previous year papers.

How should I use PYQs for Some Basic Concepts in Chemistry?

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