Some Basic Concepts of Chemistry Test

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Some Basic Concepts of Chemistry Test - 64

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Weekly Quiz Competition

Question 1
1 / -0

"Equal volumes of all gases at the same temperature and pressure contain equal number of particles." This statement is a direct consequence of:

A
Avogadro's law

B
Charles law

C
Ideal gas equation

D
Law of partial pressure

Solution

Avogadro's Law states that "Equal volumes of all gases at the same temperature and pressure contain equal number of particles."

Hence, Option "A" is the correct answer.
Question 2
1 / -0

$$40\,mL $$ gaseous mixture of $$CO , CH_4 $$ and Ne was exploded with $$ 10\,mL $$ of oxygen. On cooling the gases occupied $$36.5\,mL $$. After treatment with KOH the volume reduced by $$9\,mL $$ again on treatment with alkaline pyrogallol, the volume further reduced.
Percentage of $$CH_{4} $$ in the original mixture is:

A
$$22.5 $$

B
$$77.5 $$

C
$$7.5$$

D
$$15$$

Solution

Let the volume of $$CO , CH_4 $$ and $$Ne $$ be $$ x , y $$ and $$z$$ respectively
$$CO + \dfrac{1}{2} O_2 \rightarrow CO_2 $$ ;
$$x$$ $$ x/2$$ $$x$$

$$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O (l) $$
$$y$$ $$2y$$ $$y$$
remaining volume of $$O_2 = 10 - \dfrac{x}{2}- 2y $$

Volume after reaction :
$$ x + y + 10 - \dfrac{x}{2} - 2y + z = 36.5 $$ ............(i)
$$ x + y = 9 $$ ..........(ii)
$$ x + y + z = 40 $$ ...............(iii)
by Eq. (i) , (ii) & (iii)
Volume of $$CH_4 = 6\,mL $$
$$ \%$$ of $$CH_4 = \dfrac{6}{40} \times 100 \Rightarrow 15 $$
Question 3
1 / -0

$$4$$ mole of a mixture of Mohr's salt and $$Fe_2(SO_4)_3 $$ requires $$500\,mL $$ of $$1\,M \,K_2Cr_2O_7 $$ for complete oxidation in acidic medium. The mole % of the Mohr's salt in the mixture is:

A
$$25$$

B
$$50$$

C
$$60$$

D
$$75$$

Solution

$$Cr_2O_{7}^{2-} + 6Fe^{2+} + 14 H^+ \rightarrow 2Cr^{3+} + 6Fe{3+} + 7H_2O $$
$$( n = 1 ) $$ (Mohr's salt)
Equivalent of $$Fe^{2+} $$ = moles of Mohr's salt
= equivalent of $$K_2Cr_2O_7$$
= $$ 500 \times 10^{-3} \times 6 \times 1 = 3.0 $$
Hence. mole percent of Mohr's salt
$$ = \dfrac{3}{4} \times 100 = 75 $$
Question 4
1 / -0

For the reaction , $$2Fe(NO_3)_3 +3 Na_2CO_3 \rightarrow Fe_{2}(CO_3)_3 + 6NaNO_{3}$$
Initially if $$2.5 $$ mole of $$Fe(NO_3)_2 $$ and $$3.6 $$ mole of $$Na_{2}CO_{3} $$ is taken. If $$6.3$$ mole of $$ NaNO_{3}$$ is obtained then % yield of given reaction is :

A
$$50$$

B
$$84$$

C
$$87.5$$

D
$$100$$

Solution

$$2Fe(NO_3)_3 + 3 Na_2CO_3 \rightarrow Fe_2(CO_3)_3 + 6NaNO_3 $$
mole $$2.5$$ $$3.6$$
mole/stoichiometric coefficient $$1.25$$ $$1.2$$
Limiting reagent is $$Na_2CO_3 $$ so moles of $$NaNO_3 $$ should be formed $$ = 3.6 \times 2 = 7.2 $$

$$\%%$$ yield $$ = \dfrac{6.3}{7.2} \times 100 = 87.5 $$
Question 5
1 / -0

Which of the following fertilizers has the highest nitrogen percentage?

A
Ammonium sulphate

B
Calcium cyanamide

C
Urea

D
Ammonium nitrate

Solution

$$\% N$$ in $$(NH_{4})_{2}SO_{4} = 21.8\%$$

in $$CaCN_{2} = 35\%,$$

in $$NH_{2}CONH_{2} = 46.6\%$$

and in $$NH_{4}NO_{3} = 35\%$$
Question 6
1 / -0

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

A
$$4$$

B
$$45$$

C
$$6$$

D
$$7$$

Solution

$$Na_{2}SO_{3}.x H_{2}O$$ has 50% $$H_{2}O$$.

$$\therefore \dfrac{18x}{126+18x}=\dfrac{50}{100}$$

$$\therefore x=7$$
Question 7
1 / -0

Which of the following statements is correct about the reaction given below?
$$\displaystyle 4Fe\left ( s \right )+3O_{2}\left ( g \right )\rightarrow 2Fe_{2}O_{3}\left ( g \right )$$

A
The total mass of reactants $$=$$ Total mass of the products. It follows the law of conservation of mass.

B
The total mass of reactants $$=$$ Total mass of the products. Therefore, the law of multiple proportions is followed.

C
Amount of $$Fe_{2}O_{3}$$ can be increased by taking any one of the reactants (iron or oxygen) in excess.

D
Amount of $$Fe_{2}O_{3}$$ produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess.

Solution

Total mass of iron and oxygen in reactants $$=4 (55.85) + 3(32) =319.4\ g$$.

Total mass of iron and oxygen in product $$=2(2 \times 55.85 + 3 \times 8) =319.4\ g$$.

The total mass of iron and oxygen in reactants = the total mass of iron and oxygen in the product, therefore, it follows the law of conservation of mass.

Hence, option $$A$$ is correct.
Question 8
1 / -0

Which among the following is true about one mole of a gas?

A
It always occupies 1 litre.

B
It always occupies 2 litres.

C
It can occupy any volume at S.T.P.

D
It always occupies a fixed volume at N.T.P.
Question 9
1 / -0

1.84 g of Dolomite $$(CaMg(CO_3)_2)$$ ore was heated resulting in a residue of constant weight 0.96 g. During heating the metal of one of the products burnt with a brick red flame and the second burnt with a dazzling white flame. The approximate percentage composition of the two products in the residue are respectively

A
54 and 46

B
46 and 54

C
42 and 58

D
58 and 42

Solution
Question 10
1 / -0

$$5$$ g of crystalline salt, when rendered anhydrous, lost $$1.89$$ g of water. The formula weight of anhydrous salts is $$160$$. The number of molecules of water of crystallisation in the salt is:

A
$$1$$

B
$$2$$

C
$$3$$

D
$$5$$

Solution

Given, $$1.89$$ g of water is present in $$5$$ g of hydrated salt.

Therefore, weight of anhydrous salt is $$(5 -1.89)$$ g $$= 3.11$$ g.

No of moles of anhydrous salt $$ = \dfrac{3.11}{160} = 0.02 moles$$

No of moles of water $$= \dfrac{1.89}{18} = 0.1 moles$$

Ratio of anhydrous salt to water,

Salt: Water $$= 0.02 : 0.1$$

$$1:5$$

Therefore, no of molecules of water $$=5$$.

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Re-Attempt Weekly Quiz Competition

Some Basic Concepts of Chemistry Test - 64

Result

Some Basic Concepts of Chemistry Test - 64

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SHARING IS CARING

Question 1

Avogadro's law

Charles law

Ideal gas equation

Law of partial pressure

Solution

Question 2

$$22.5 $$

$$77.5 $$

$$7.5$$

$$15$$

Solution

Question 3

$$25$$

$$50$$

$$60$$

$$75$$

Solution

Question 4

$$50$$

$$84$$

$$87.5$$

$$100$$

Solution

Question 5

Ammonium sulphate

Calcium cyanamide

Urea

Ammonium nitrate

Solution

Question 6

$$4$$

$$45$$

$$6$$

$$7$$

Solution

Question 7

The total mass of reactants $$=$$ Total mass of the products. It follows the law of conservation of mass.

The total mass of reactants $$=$$ Total mass of the products. Therefore, the law of multiple proportions is followed.

Amount of $$Fe_{2}O_{3}$$ can be increased by taking any one of the reactants (iron or oxygen) in excess.

Amount of $$Fe_{2}O_{3}$$ produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess.

Solution

Question 8

It always occupies 1 litre.

It always occupies 2 litres.

It can occupy any volume at S.T.P.

It always occupies a fixed volume at N.T.P.

Question 9

54 and 46

46 and 54

42 and 58

58 and 42

Solution

Question 10

$$1$$

$$2$$

$$3$$

$$5$$

Solution

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