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.

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An organic compound made of C, H and N contains 20% nitrogen. What will be its molecular mass if it contains only one nitrogen atom in it ?

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Important Questions on Some Basic Concepts of Chemistry

HARD

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

In Carius method of estimation of halogens,

250 mg

of an organic compound gave

141 mg AgBr

. What is the percentage of bromine in the compound (atomic mass of

Ag = 108

and atomic number of

Br = 80

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

The common isotopes of carbon are

{}^{12}C

and

{}^{13}C

. The average mass of carbon is

12.01115 amu

. What is the abundance of the

{}^{13}C

isotope?

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

Two elements

A

and

B

which form

0.15

moles of

A_{2} B

and

{AB}_{3}

type compounds. If one mole of each

A_{2} B

and

{AB}_{3}

weigh equally, then the atomic weight of

A

is____times of atomic weight of

B

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

A sample of a hydrate of barium chloride weighing 61 g was heated until all the water of hydration is removed. The dried sample weighed 52 g. The formula of the hydrated salt is: (atomic mass, Ba = 137 amu, Cl = 35.5 amu)

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

One mole of dioxygen gas at

STP

is equal to

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular 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:

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

Which symbol replaced the unit of atomic mass, amu?

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

The percentage of nitrogen by mass in ammonium sulphate is closest to (atomic masses H = 1, N = 14, O = 16, S = 32)

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

The unit of atomic mass,

amu

is replaced by

u

, here

u

stands for

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

What will be the mass of one atom of

{}^{12}C

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular 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?

HARD

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

Natural abundances of

^{12} C

and

^{13} C

isotopes of carbon are

99 %

and

1 %

respectively. Assuming they only contributes to the molecular weight of

C_{2} F_{4}

, the percentage of

C_{2} F_{4}

having a molecular mass of

101

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular 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

EASY

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

The number of water molecules is maximum in

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular 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}

)

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

An amount of

18 g

glucose corresponds to:

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

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

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

Calculate mass of

3.01 \times 10^{24}

atoms of an element having atomic mass

21.13

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Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

The average molar mass of chlorine is

35.5 g {mol}^{- 1}

. The ratio of

{}^{35}{Cl}

{}^{37}{Cl}

in naturally occurring chlorine is close to :

MEDIUM

Chemistry>Physical Chemistry>Some Basic Concepts of Chemistry>Atomic and Molecular Masses

Chlorine has two naturally occurring isotopes.

^{35} C l

and

^{37} C l

. If the atomic mass if

C l

is 35.45, the ratio of natural abundance of

^{35} C l

and

^{37} C l

is closest to

An organic compound made of C, H and N contains 20% nitrogen. What will be its molecular mass if it contains only one nitrogen atom in it ?

Important Questions on Some Basic Concepts of Chemistry

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