If Avogadro number N A , is changed from 6.022 × 10 23 m o l - 1 to 6.022 × 10 20 m o l - 1 , this would change:

The definition of mass in units of grams

The ratio of chemical species to each other in a balanced equation.

The ratio of elements to each other in a compound.

5 moles of A B 2 weigh 125 × 10 - 3 k g and 10 moles of A 2 B 2 weigh 300 × 10 - 3 k g . The molar mass of A ( M A ) and molar mass of B ( M B ) in k g m o l - 1 are:

M A = 5 × 10 - 3 and M B = 10 × 10 - 3

M A = 25 × 10 - 3 and M B = 50 × 10 - 3

M A = 50 × 10 - 3 and M B = 25 × 10 - 3

M A = 10 × 10 - 3 and M B = 5 × 10 - 3

MEDIUM

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The molality of a $10 % (v / v)$ solution of di-bromine solution in ${CCl}_{4}$ (carbon tetrachloride) is $' x' . x =________\times 10^{- 2} M$ . (Nearest integer)

[Given: molar mass of ${Br}_{2} = 160 g {mol}^{- 1}$

atomic mass of $C = 12 g {mol}^{- 1}$

atomic mass of $Cl = 35.5 g {mol}^{- 1}$

density of dibromine = $3.2 g {cm}^{- 3}$

density of ${CCl}_{4} = 1.6 g {cm}^{- 3}$ ]

Important Questions on Some Basic Concepts of Chemistry

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The volume of oxygen at STP required to burn 2.4 g of carbon completely is:

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

If Avogadro number

N_{A}

, is changed from

6.022 \times 10^{23} m o l^{- 1}

6.022 \times 10^{20} m o l^{- 1}

, this would change:

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

An unknown chlorohydrocarbon has 3.55 % of chlorine. If each molecule of the hydrocarbon has one chlorine atom only; chlorine atoms present in 1 g of chlorohydrocarbon are :(Atomic wt. of

Cl = 35 .5 u;

Avogadro constant

= 6 .023 \times 10^{23} {mol}^{- 1}

)

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The ratio of masses of oxygen and nitrogen in a particular gaseous mixture is 1 : 4. The ratio of number of their molecules is:

HARD

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

An organic compound contains

C, H

and

S

. The minimum molecular weight of the compound containing

8 %

Sulphur is

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The amount of oxygen in

3.6

moles of water is:

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

A mixture of gases contains

H_{2}

and

O_{2}

gases in the ratio of

1 : 4

(w/w). What is the molar ratio of the two gases in the mixture?

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

Which one of the following will have the largest number of atoms?

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The percentage composition of carbon by mole in methane is:

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

5

moles of

A B_{2}

weigh

125 \times 10^{- 3} k g

and

10

moles of

A_{2} B_{2}

weigh

300 \times 10^{- 3} k g

. The molar mass of A

(M_{A})

and molar mass of

B (M_{B})

k g {m o l}^{- 1}

are:

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

Ferrous sulphate heptahydrate is used to fortify foods with iron. The amount (in grams) of the salt required to achieve

10 p p m

of iron in

100 k g

of wheat is ____________. (Up to two decimal place)
Atomic weight:

F e = 55.85; S = 32.00; O = 16.00

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The number of water molecules is maximum in

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The flocculation value of

H C l

for arsenic sulphide

s o l

30 m m o l L^{- 1}

. If

H_{2} S O_{4}

is used for the flocculation of arsenic sulphide, the amount, in grams, of

H_{2} S O_{4}

250 m l

required for the above purpose is ________. (Round off to two digits after decimal.)
(molecular mass of

H_{2} {S O}_{4} = 98 g / m o l

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

An amount of

18 g

glucose corresponds to:

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The first and second ionisation enthalpies of a metal are

496

and

4560 k J m o l^{- 1}

, respectively. How many moles of

H C l

and

H_{2} S O_{4},

respectively, will be needed to react completely with

1

mole of the metal hydroxide?

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

Which one of the followings has maximum number of atoms?

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

0.023 \times 10^{22}

molecules are present in

10 g

of a substance

{}^{'}x^{'} .

The molarity of a solution containing

5 g

of substance 'x' in 2 L solution is

_________\times 10^{- 3}

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

In which case the number of molecules of water maximum?

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

Suppose the elements

X

and

Y

combine to form two compounds

X Y_{2}

and

X_{3} Y_{2}

. When

0.1 mole

X Y_{2}

weighs

10 g

and

0.05 mole

X_{3} Y_{2}

weighs

9 g

, the atomic weights of

X

and

Y

are

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Mole Concept and Molar Masses

The amount of sugar

(C_{12} H_{22} O_{11})

required to prepare

2 L

of its

0 .1 M

aqueous solution is:

Important Questions on Some Basic Concepts of Chemistry

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