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Some Basic Concepts of Chemistry

185631 The number of significant figures in $6.02 \times 10^{23}$ is

1

23

2

3

3

4

4

26

Explanation:

When numbers are written in scientific notation, then the number of digits between $1$ and $10$ gives the number of significant figures.
Thus, the number $6.02 \times 10^{23}$ contains $3$ significant figures.
All the three digits $(6, 0$ and $2)$ are significant.

Some Basic Concepts of Chemistry

185632 The prefix zepto stands for

1

10^{9}

2

10^{- 12}

3

10^{- 15}

4

10^{- 21}

Explanation:

Zepto is a unit prefix in the metric system denoting a factor of $10^{- 21}$ .
$1$ zepto $= 10^{- 21}$

Some Basic Concepts of Chemistry

185736 The total number of gm-molecules of $S O_{2} C l_{2}$ in $13.5 g$ of sulphuryl chloride is

1

0.1

2

0.2

3

0.3

4

0.4

Explanation:

(a) Molecular weight of $S O_{2} C l_{2}$
$= 32 + 32 + 2 \times 35.5$ = $135 g m$
$135 g m$ of $S O_{2} C l_{2}$ $= 1 g m$ molecule
$∴$ $13.5 g m$ of $S O_{2} C l_{2}$ $= \frac{1}{135} \times 13.5 = 0.1$ .

Some Basic Concepts of Chemistry

185775 Hydrochloric acid solutions $A$ and $B$ have concentration of $0.5 N$ and $0.1 N$ respectively. The volume of solutions $A$ and $B$ required to make $2$ litres of $0.2 N$ hydrochloric are

1

0.5 l

of

A

+ 1.5 l

of

B

2

1.5 l

of

A

+ 0.5 l

of

B

3

1.0 l

of

A

+ 1.0 l

of

B

4

0.75 l

of

A

+ 1.25 l

of

B

Explanation:

(a) $N V = N_{1} V_{1} + N_{2} V_{2}$
$0.2 \times 2 = 0.5 x + 0.1 (2 - x)$
$0.4 = 0.5 x + 0.2 - 0.1 x$
$0.2 = 0.4 x$
$x = \frac{1}{2} L = 0.5 L$

Some Basic Concepts of Chemistry

185937 A gas is found to contain $2.8 g$ nitrogen and $3.2 g$ oxygen, simplest formula of the compound is

1

N_{2} O

2

N O

3

N_{2} O_{3}

4

N O_{2}

Explanation:

Element Mass Moles Simple ratio
$N$ $2.8$ $\frac{2.8}{14} = 0.2 = 1$
$O$ $3.2 g$ $\frac{3.2}{16} = 0.2 = 1$
Simplest formula of the compound $= N O$

Some Basic Concepts of Chemistry

185631 The number of significant figures in $6.02 \times 10^{23}$ is

1

23

2

3

3

4

4

26

Explanation:

When numbers are written in scientific notation, then the number of digits between $1$ and $10$ gives the number of significant figures.
Thus, the number $6.02 \times 10^{23}$ contains $3$ significant figures.
All the three digits $(6, 0$ and $2)$ are significant.

Some Basic Concepts of Chemistry

185632 The prefix zepto stands for

1

10^{9}

2

10^{- 12}

3

10^{- 15}

4

10^{- 21}

Explanation:

Zepto is a unit prefix in the metric system denoting a factor of $10^{- 21}$ .
$1$ zepto $= 10^{- 21}$

Some Basic Concepts of Chemistry

185736 The total number of gm-molecules of $S O_{2} C l_{2}$ in $13.5 g$ of sulphuryl chloride is

1

0.1

2

0.2

3

0.3

4

0.4

Explanation:

(a) Molecular weight of $S O_{2} C l_{2}$
$= 32 + 32 + 2 \times 35.5$ = $135 g m$
$135 g m$ of $S O_{2} C l_{2}$ $= 1 g m$ molecule
$∴$ $13.5 g m$ of $S O_{2} C l_{2}$ $= \frac{1}{135} \times 13.5 = 0.1$ .

Some Basic Concepts of Chemistry

185775 Hydrochloric acid solutions $A$ and $B$ have concentration of $0.5 N$ and $0.1 N$ respectively. The volume of solutions $A$ and $B$ required to make $2$ litres of $0.2 N$ hydrochloric are

1

0.5 l

of

A

+ 1.5 l

of

B

2

1.5 l

of

A

+ 0.5 l

of

B

3

1.0 l

of

A

+ 1.0 l

of

B

4

0.75 l

of

A

+ 1.25 l

of

B

Explanation:

(a) $N V = N_{1} V_{1} + N_{2} V_{2}$
$0.2 \times 2 = 0.5 x + 0.1 (2 - x)$
$0.4 = 0.5 x + 0.2 - 0.1 x$
$0.2 = 0.4 x$
$x = \frac{1}{2} L = 0.5 L$

Some Basic Concepts of Chemistry

185937 A gas is found to contain $2.8 g$ nitrogen and $3.2 g$ oxygen, simplest formula of the compound is

1

N_{2} O

2

N O

3

N_{2} O_{3}

4

N O_{2}

Explanation:

Element Mass Moles Simple ratio
$N$ $2.8$ $\frac{2.8}{14} = 0.2 = 1$
$O$ $3.2 g$ $\frac{3.2}{16} = 0.2 = 1$
Simplest formula of the compound $= N O$

Some Basic Concepts of Chemistry

185631 The number of significant figures in $6.02 \times 10^{23}$ is

1

23

2

3

3

4

4

26

Explanation:

When numbers are written in scientific notation, then the number of digits between $1$ and $10$ gives the number of significant figures.
Thus, the number $6.02 \times 10^{23}$ contains $3$ significant figures.
All the three digits $(6, 0$ and $2)$ are significant.

Some Basic Concepts of Chemistry

185632 The prefix zepto stands for

1

10^{9}

2

10^{- 12}

3

10^{- 15}

4

10^{- 21}

Explanation:

Zepto is a unit prefix in the metric system denoting a factor of $10^{- 21}$ .
$1$ zepto $= 10^{- 21}$

Some Basic Concepts of Chemistry

185736 The total number of gm-molecules of $S O_{2} C l_{2}$ in $13.5 g$ of sulphuryl chloride is

1

0.1

2

0.2

3

0.3

4

0.4

Explanation:

(a) Molecular weight of $S O_{2} C l_{2}$
$= 32 + 32 + 2 \times 35.5$ = $135 g m$
$135 g m$ of $S O_{2} C l_{2}$ $= 1 g m$ molecule
$∴$ $13.5 g m$ of $S O_{2} C l_{2}$ $= \frac{1}{135} \times 13.5 = 0.1$ .

Some Basic Concepts of Chemistry

185775 Hydrochloric acid solutions $A$ and $B$ have concentration of $0.5 N$ and $0.1 N$ respectively. The volume of solutions $A$ and $B$ required to make $2$ litres of $0.2 N$ hydrochloric are

1

0.5 l

of

A

+ 1.5 l

of

B

2

1.5 l

of

A

+ 0.5 l

of

B

3

1.0 l

of

A

+ 1.0 l

of

B

4

0.75 l

of

A

+ 1.25 l

of

B

Explanation:

(a) $N V = N_{1} V_{1} + N_{2} V_{2}$
$0.2 \times 2 = 0.5 x + 0.1 (2 - x)$
$0.4 = 0.5 x + 0.2 - 0.1 x$
$0.2 = 0.4 x$
$x = \frac{1}{2} L = 0.5 L$

Some Basic Concepts of Chemistry

185937 A gas is found to contain $2.8 g$ nitrogen and $3.2 g$ oxygen, simplest formula of the compound is

1

N_{2} O

2

N O

3

N_{2} O_{3}

4

N O_{2}

Explanation:

Element Mass Moles Simple ratio
$N$ $2.8$ $\frac{2.8}{14} = 0.2 = 1$
$O$ $3.2 g$ $\frac{3.2}{16} = 0.2 = 1$
Simplest formula of the compound $= N O$

Some Basic Concepts of Chemistry

185631 The number of significant figures in $6.02 \times 10^{23}$ is

1

23

2

3

3

4

4

26

Explanation:

When numbers are written in scientific notation, then the number of digits between $1$ and $10$ gives the number of significant figures.
Thus, the number $6.02 \times 10^{23}$ contains $3$ significant figures.
All the three digits $(6, 0$ and $2)$ are significant.

Some Basic Concepts of Chemistry

185632 The prefix zepto stands for

1

10^{9}

2

10^{- 12}

3

10^{- 15}

4

10^{- 21}

Explanation:

Zepto is a unit prefix in the metric system denoting a factor of $10^{- 21}$ .
$1$ zepto $= 10^{- 21}$

Some Basic Concepts of Chemistry

185736 The total number of gm-molecules of $S O_{2} C l_{2}$ in $13.5 g$ of sulphuryl chloride is

1

0.1

2

0.2

3

0.3

4

0.4

Explanation:

(a) Molecular weight of $S O_{2} C l_{2}$
$= 32 + 32 + 2 \times 35.5$ = $135 g m$
$135 g m$ of $S O_{2} C l_{2}$ $= 1 g m$ molecule
$∴$ $13.5 g m$ of $S O_{2} C l_{2}$ $= \frac{1}{135} \times 13.5 = 0.1$ .

Some Basic Concepts of Chemistry

185775 Hydrochloric acid solutions $A$ and $B$ have concentration of $0.5 N$ and $0.1 N$ respectively. The volume of solutions $A$ and $B$ required to make $2$ litres of $0.2 N$ hydrochloric are

1

0.5 l

of

A

+ 1.5 l

of

B

2

1.5 l

of

A

+ 0.5 l

of

B

3

1.0 l

of

A

+ 1.0 l

of

B

4

0.75 l

of

A

+ 1.25 l

of

B

Explanation:

(a) $N V = N_{1} V_{1} + N_{2} V_{2}$
$0.2 \times 2 = 0.5 x + 0.1 (2 - x)$
$0.4 = 0.5 x + 0.2 - 0.1 x$
$0.2 = 0.4 x$
$x = \frac{1}{2} L = 0.5 L$

Some Basic Concepts of Chemistry

185937 A gas is found to contain $2.8 g$ nitrogen and $3.2 g$ oxygen, simplest formula of the compound is

1

N_{2} O

2

N O

3

N_{2} O_{3}

4

N O_{2}

Explanation:

Element Mass Moles Simple ratio
$N$ $2.8$ $\frac{2.8}{14} = 0.2 = 1$
$O$ $3.2 g$ $\frac{3.2}{16} = 0.2 = 1$
Simplest formula of the compound $= N O$

Some Basic Concepts of Chemistry

185631 The number of significant figures in $6.02 \times 10^{23}$ is

1

23

2

3

3

4

4

26

Explanation:

When numbers are written in scientific notation, then the number of digits between $1$ and $10$ gives the number of significant figures.
Thus, the number $6.02 \times 10^{23}$ contains $3$ significant figures.
All the three digits $(6, 0$ and $2)$ are significant.

Some Basic Concepts of Chemistry

185632 The prefix zepto stands for

1

10^{9}

2

10^{- 12}

3

10^{- 15}

4

10^{- 21}

Explanation:

Zepto is a unit prefix in the metric system denoting a factor of $10^{- 21}$ .
$1$ zepto $= 10^{- 21}$

Some Basic Concepts of Chemistry

185736 The total number of gm-molecules of $S O_{2} C l_{2}$ in $13.5 g$ of sulphuryl chloride is

1

0.1

2

0.2

3

0.3

4

0.4

Explanation:

(a) Molecular weight of $S O_{2} C l_{2}$
$= 32 + 32 + 2 \times 35.5$ = $135 g m$
$135 g m$ of $S O_{2} C l_{2}$ $= 1 g m$ molecule
$∴$ $13.5 g m$ of $S O_{2} C l_{2}$ $= \frac{1}{135} \times 13.5 = 0.1$ .

Some Basic Concepts of Chemistry

185775 Hydrochloric acid solutions $A$ and $B$ have concentration of $0.5 N$ and $0.1 N$ respectively. The volume of solutions $A$ and $B$ required to make $2$ litres of $0.2 N$ hydrochloric are

1

0.5 l

of

A

+ 1.5 l

of

B

2

1.5 l

of

A

+ 0.5 l

of

B

3

1.0 l

of

A

+ 1.0 l

of

B

4

0.75 l

of

A

+ 1.25 l

of

B

Explanation:

(a) $N V = N_{1} V_{1} + N_{2} V_{2}$
$0.2 \times 2 = 0.5 x + 0.1 (2 - x)$
$0.4 = 0.5 x + 0.2 - 0.1 x$
$0.2 = 0.4 x$
$x = \frac{1}{2} L = 0.5 L$

Some Basic Concepts of Chemistry

185937 A gas is found to contain $2.8 g$ nitrogen and $3.2 g$ oxygen, simplest formula of the compound is

1

N_{2} O

2

N O

3

N_{2} O_{3}

4

N O_{2}

Explanation:

Element Mass Moles Simple ratio
$N$ $2.8$ $\frac{2.8}{14} = 0.2 = 1$
$O$ $3.2 g$ $\frac{3.2}{16} = 0.2 = 1$
Simplest formula of the compound $= N O$

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