Some Basic Concepts of Chemistry Test

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Some Basic Concepts of Chemistry Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

If an equivalent weight of an element is $$32$$, then the percentage of oxygen in its oxide is :

A
$$16$$

B
$$40$$

C
$$32$$

D
$$20$$

Solution

If an equivalent weight of an element is $$32$$, then it will combine with $$8$$ g of oxygen to form metal oxide (from the definition of equivalent weight).
So, % of oxygen $$=8\times \dfrac{100}{40} = 20$$
Question 2
1 / -0

Which of the following has the largest mass of carbon per gram?

A
$$H_2CO_3$$

B
$$CH_3CO_2H$$

C
$$CH_3OH$$

D
$$CH_3CH_2OH$$

Solution

Compound Mass of carbon per gram
(a)$$H_2CO_3 = \dfrac{12}{62}g$$ carbon
(b)$$CH_3CO_2H = \dfrac{24}{60}g$$ carbon
(c)$$CH_3OH = \dfrac{12}{32}g$$ carbon
(d)$$CH_3CH_2OH = \dfrac{24}{40}g$$ carbon (maximum)
Hence, largest mass of carbon per gram is for $$CH_3CH_2OH$$.
Question 3
1 / -0

All the substances listed below are fertilizers that contribute nitrogen to the soil. Which of these is the richest source of nitrogen on a mass percentage basis?

A
Urea, $$(NH_2)_2CO$$

B
Ammonium nitrate, $$NH_4NO_3$$

C
Guanidine, $$HNC(NH_2)_2$$

D
Ammonia, $$NH_3$$

Solution

Compound %N
Urea $$(NH_2)_2CO$$      $$28\times 100/60 = 46.67\%$$
Ammonia $$NH_3$$     $$14\times 100/17 = 82.35\%$$
Ammonium nitrate $$NH_4NO_3 $$    $$28\times 100/80 =35\%$$
Guanidine $$HNC(NH_2)_2$$ $$42\times 100/59 = 71.18\%$$
Hence, ammonia is the richest source of nitrogen on a mass percentage basis.
Question 4
1 / -0

What is the mass percent of carbon in carbon dioxide?

A
$$0.034$$%

B
$$27.27$$%

C
$$3.4$$%

D
$$28.7$$%

Solution

Molecular formula of carbon dioxide is $$CO_2$$.
Molar mass of carbon dioxide is $$12+2(16)=44$$ g/mol.
Mass percentage of carbon in carbon dioxide is $$\dfrac {12} {44} \times 100 =27.27\%$$.
Question 5
1 / -0

Cost of a fertilizer is based on the percentage of nitrogen in it. Which of the fertilizers should be priced maximum?

A
$$ NH_4NO_3 $$

B
$$ NH_2CONH_2 $$

C
$$ KNO_3 $$

D
None of the above

Solution

Molecular weight of $$NH_4NO_3$$ is 80, $$NH_2CONH_2$$ is 60, and $$KNO_3$$ is 101.

Percentage of $$N$$ in:

$$NH_4NO_3=\displaystyle\dfrac{28\times 100}{80} = 35\% $$

$$NH_2CONH_2=\displaystyle\frac{28\times 100}{60} = 46.7\% $$

$$KNO_3=\displaystyle\frac{14}{101}\times 100 = 13.9\%$$

Urea, having the highest percentage of nitrogen, should have the highest cost.

Hence, option B is correct.
Question 6
1 / -0

Cortisone is a molecular substance containing $$21$$ atoms of carbon per molecule. The mass percentage of carbon in cortisone is $$69.98\%$$. It's molar mass is:

A
$$176.5$$

B
$$252.2$$

C
$$287.6$$

D
$$360.1$$

Solution

Let molar mass be$$=M$$

Mass of $$21$$ carbon atoms$$=252$$

$$\%$$ of carbon $$=\displaystyle\frac{252\times 100}{M}=69.98$$

but % of carbon = 69.98 %

$$\therefore M=360.1$$

Hence, the correct option is $$D$$
Question 7
1 / -0

A certain metal sulphide, $$MS_2$$, is used extensively as a high temperature lubricant. If $$MS_2$$ is $$40.06\%$$ by mass of sulphur, metal $$M$$ has atomic mass :

A
$$160$$ amu

B
$$64$$ amu

C
$$40$$ amu

D
$$96$$ amu

Solution

Molecular weight of $$MS_2=2S + M$$
$$\dfrac {64}{M+64} = 0.4006$$
$$\therefore M=96$$
Question 8
1 / -0

Which has maximum percentage of $$Cl$$?

A
$$C_6H_6Cl_6$$

B
$$CHCl_3$$

C
$$C_6H_5Cl$$

D
$$CH_3Cl$$

Solution

Compound    % Cl
$$C_6H_6Cl_6$$    $$6\times \dfrac{35.5}{78} + 35.5\times 6 = \dfrac{213}{291} = 73.2\%$$

$$CHCl_3$$       $$3\times \dfrac{35.5}{119.5} = \dfrac{106.5}{119.5} = 89.1\%$$

$$C_6H_5Cl$$    $$\dfrac{35.5}{112.5} = 31.6\% $$

$$CH_3Cl$$ $$\dfrac{35.5}{50.5} = 70.3\%$$
Hence, the maximum percentage of chlorine is present in $$CHCl_3$$.
Question 9
1 / -0

$$Na_2SO_3\cdot xH_2O$$ has $$50\%$$ $$H_2O$$ by mass. Hence, $$x$$ is :

A
$$4$$

B
$$5$$

C
$$6$$

D
$$7$$

Solution

Molecular mass of $$Na_2SO_3\cdot xH_2O=126+18x$$
Hence, $$\displaystyle\frac{18x}{126+18x}=0.5$$ (given)
$$\therefore x=7$$

Question 10

1 / -0

Which pair has the same percentage of carbon?

$$CH_3COOH \: and \: C_6H_{12}O_6$$

$$CH_3COOH \: and \: C_{12}H_{22}O_{11}$$

$$CH_3COOH \: and \: C_2H_5OH$$

$$C_6H_{12}O_6 \: and \: C_{12}H_{22}O_{11}$$

Solution

The table below shows the simple ratio between the number of atoms.

$$Compound$$	$$C$$	$$H$$	$$O$$
$$CH_3COOH$$	1	2	1
$$C_6H_12O_6$$	1	2	1
$$C_2H_5OH$$	2	6	1
$$C_{12}H_{22}O_{11}$$	12	22	11

So, $$CH_3COOH$$ and $$C_6H_{12}O_6$$ have same % of $$C$$.

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Re-Attempt Weekly Quiz Competition

Some Basic Concepts of Chemistry Test - 23

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Some Basic Concepts of Chemistry Test - 23

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Question 1

$$16$$

$$40$$

$$32$$

$$20$$

Solution

Question 2

$$H_2CO_3$$

$$CH_3CO_2H$$

$$CH_3OH$$

$$CH_3CH_2OH$$

Solution

Question 3

Urea, $$(NH_2)_2CO$$

Ammonium nitrate, $$NH_4NO_3$$

Guanidine, $$HNC(NH_2)_2$$

Ammonia, $$NH_3$$

Solution

Question 4

$$0.034$$%

$$27.27$$%

$$3.4$$%

$$28.7$$%

Solution

Question 5

$$ NH_4NO_3 $$

$$ NH_2CONH_2 $$

$$ KNO_3 $$

None of the above

Solution

Question 6

$$176.5$$

$$252.2$$

$$287.6$$

$$360.1$$

Solution

Question 7

$$160$$ amu

$$64$$ amu

$$40$$ amu

$$96$$ amu

Solution

Question 8

$$C_6H_6Cl_6$$

$$CHCl_3$$

$$C_6H_5Cl$$

$$CH_3Cl$$

Solution

Question 9

$$4$$

$$5$$

$$6$$

$$7$$

Solution

Question 10

$$CH_3COOH \: and \: C_6H_{12}O_6$$

$$CH_3COOH \: and \: C_{12}H_{22}O_{11}$$

$$CH_3COOH \: and \: C_2H_5OH$$

$$C_6H_{12}O_6 \: and \: C_{12}H_{22}O_{11}$$

Solution

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