Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation: 2 NaOH + CuSO 4 → Na 2 SO 4 + Cu ( OH ) 2 ↓ i) What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide? [ H = 1 , O = 16 , Na = 23 , S = 32 , Cu = 64 ] (ii) What is the colour of the precipitate formed?

(i) 2 NaOH + CuSO 4 → Na 2 SO 4 + Cu ( OH ) 2 ↓ Molecular mass of sodium hydroxide = 2 ( 23 + 16 + 1 ) = 80 g Molecular mass of copper hydroxide = 64 + 32 + 2 = 98 g 98 g of Cu ( OH ) 2 is precipitated by using 80 g of NaOH . x g of Cu ( OH ) 2 is precipitated by using 200 g of NaOH . x = 98 80 × 200 g = 245 g of Cu ( OH ) 2 (ii) A light blue precipitate of copper hydroxide will be formed.

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Number of atoms of oxygen present in 10.6 g of ${N a}_{2} {C O}_{3}$ will be

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Important Questions on Some Basic Concepts of Chemistry

EASY

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

Calculate the weight of

10^{22}

atoms of carbon. [

C = 12

, Avogadro’s No.=

6 \times 10^{23}

]

EASY

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

MEDIUM

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

EASY

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

A and B react to produce C according to the following chemical equation
$2 A + B \to 2 C$

A, B and C are the formulas for three gaseous substances. The vapour densities of A and B are 32 and 16 respectively. Find out the vapour density of C.

EASY

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 :

EASY

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

The molecular mass of methane $({CH}_{4})$ is $16 u$ .

What is the mass of 1 GMM of CH4

EASY

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?

HARD

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

3 g

of acetic acid is added to

250 m L

0.1 M H C l

and the solution made up to

500 m L

. To

20 m L

of this solution

\frac{1}{2} m L

5 M N a O H

is added. The

p H

of the solution is ________
[Given:

p K a

of acetic acid

= 4.75,

molar mass of acetic acid

60 g / m o l, \log 3 = 0.4771

, Neglect any changes in volume]

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

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 is gram atomic mass?

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

EASY

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

Calculate:

How many gram atoms of sodium is present in $115 g$ sodium?

MEDIUM

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

Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation:

$2 NaOH + {CuSO}_{4} \to {Na}_{2} {SO}_{4} + Cu {(OH)}_{2} ↓$

i) What mass of copper hydroxide is precipitated by using $200 gm$ of sodium hydroxide?

$[H = 1, O = 16, Na = 23, S = 32, Cu = 64]$

(ii) What is the colour of the precipitate formed?

EASY

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

Calculate:

Mass of 5 gram atoms of calcium.
[Hint: Gram atoms mass: $Ca = 40 g$ ]

EASY

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

In which case the number of molecules of water maximum?

MEDIUM

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

Consider an imaginary ion

{}_{22}^{48}X^{3 -}

. The nucleus contains '

a

%

more neutrons than the number of electrons in the ion. The value of '

a

' is

EASY

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

What will be the mass of one atom of

{}^{12}C

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

EASY

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

Which symbol replaced the unit of atomic mass, amu?

Number of atoms of oxygen present in 10.6 g of Na2CO3 will be

Important Questions on Some Basic Concepts of Chemistry

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Number of atoms of oxygen present in 10.6 g of ${N a}_{2} {C O}_{3}$ will be