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

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The simplest formula of the compound containing nitrogen ( $14 g$ ) for each $40 g$ of oxygen is

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Important Questions on Some Basic Concepts of Chemistry

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

Mass % of carbon in ethanol is

HARD

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

EASY

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

1.85 g

sample of an arsenic-containing pesticide was chemically converted to

{AsO}_{4}^{3 -}

(atomic mass of

As = 74.9

) and titrated with

{Pb}^{2 +}

to form

{Pb}_{3} {({AsO}_{4})}_{2}

. If

20 mL of 0.1 M {Pb}^{2 +}

is required to reach the equivalence point, the mass percentages of arsenic in the pesticide sample is closest to

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

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

1.25 g of a metal (M) reacts with oxygen completely to produce 1.68 g of metal oxide. The empirical formula of the metal oxide is [Molar mass of M and O are

69.7 g m o l^{- 1}

and

16.0 g m o l^{- 1}

, respectively]

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

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

Complex A has a composition of

H_{12} O_{6} {Cl}_{3} C r

. If the complex on treatment with conc.

H_{2} {SO}_{4}

loses

13.5 %

of its original mass, the correct molecular formulas of

A

is:
[Given : atomic mass of

C r = 52

amu and

Cl = 35

amu]

EASY

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

The percentage composition of carbon by mole in methane is:

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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:

HARD

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

One mole of one of the sodium salts listed below, having carbon content close to

14.3 %

produces

1

mole of carbon dioxide upon heating

(Atomic masses : Na = 23, H = 1, C = 12, O = 16)

. The salt is

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

The number of water molecules is maximum in

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

The ratio of mass percent of

C and H

of an organic compound

(C_{X} H_{Y} O_{Z})

6 : 1 .

If one molecule of the above compound

(C_{X} H_{Y} O_{Z})

contains half as much oxygen as required to burn one molecule of compound

C_{X} H_{Y}

completely to

{CO}_{2}

and

H_{2} O .

The empirical formula of the compound

C_{X} H_{Y} O_{Z}

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

A compound has the following composition by weight;

N a = 18.60 %, S = 25.80 %, H = 4.02 %

and

O = 51.58 %

Assuming that all the hydrogen atoms in the compound are part of water of crystallization, the correct molecular formula of the compound is

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

An organic compound contains

24 %

carbon,

4 %

hydrogen and remaining chlorine. Its empirical formula is

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

The empirical formula and molecular mass of a compound are

{CH}_{2} O

and

180 g

respectively. The molecular formula of the compound will be

EASY

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

In an estimation of bromine by Carius method,

1.6 g

of an organic compound gave

1.88 g

AgBr

. The mass percentage of bromine in the compound is

\dots . .

(

Atomic mass,

Ag = 108, Br = 80 {gmol}^{- 1}

EASY

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

In which case the number of molecules of water maximum?

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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

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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:

The simplest formula of the compound containing nitrogen (14 g) for each40 g of oxygen is

Important Questions on Some Basic Concepts of Chemistry

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The simplest formula of the compound containing nitrogen ( $14 g$ ) for each $40 g$ of oxygen is