Some Basic Concepts Of Chemistry Test 12

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Some Basic Concepts Of Chemistry Test 12

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Weekly Quiz Competition

Question 1
1 / -0

4.88 g of KCIO₃ when heated produced 1.92 g of O₂ and 2.96 gof KCl. Which ofthe following statements regarding the experiment is correct?

A
The result illustrates the law of conservation of mass

B
The result of illustrates the law of multiple proportions

C
The result illustrates the law of constant proportion

D
None of the above laws is followed

Solution

Since, mass of the products (2.96 + 1.92) is equal to mass of the reactant, this illustrates the law of conservation of mass.
Question 2
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How much mass of silver nitrates will react with 5.85 g of sodium chloride to produce 14.35 g of silver chloride and 8.5 g of sodium nitrates if law of conservation of mass is followed?

A
22.85 g

B
108 g

C
17.0 g

D
28.70 g

Solution

x + 5.85 = 8.5 + 14.35 ⇒ x = 17 g
Question 3
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What mass of hydrochloric acid is needed to decompose 50 g of limestone?

A
36.5 g

B
73 g

C
50 g

D
100 g

Solution

100 g of CaCO₃ requires 73 g of HCl
∴ 50 g of CaCO₃requires 73/100 x 50 = 36.5 g of HCl
Question 4
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What mass of sodium chloride would be decomposed by 9.8 g of sulphuric acid if 12 g of sodium bisulphate and 2.75 g of hydrogen chloride were produced in a reaction?

A
14.75 g

B
3.8 g

C
4.95 g

D
2.2 g

Solution

x + 9.8 = 12 + 2.75 ⇒ x = 4.95g
Question 5
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In an experiment, 2.4g of iron oxide on reduction with hydrogen gave 1.68 g of iron. In another experiment, 2.9 g of iron oxide gave 2.09 g of iron on reduction.Which law is illustrated from the above data?

A
Law of constant proportions

B
Law of multiple proportions

C
Law of reciprocal proportions

D
Law of conservation of mass

Solution

In first experiment,
2.4 g of iron oxide gave 1.68 g of iron.
Mass of iron oxide = 2.4 g
Mass of iron = 1.68 g
Mass of oxygen = 2.4 - 1.68 = 0.72
Ratio of masses of iron and oxygen = 1.68/0.72 = 7:3
In second experiment,
Mass of iron oxide = 2.9 g
Mass of iron = 2.09 g
Mass of oxygen = 2.9 - 2.09 = 0.81
Ratio of masses of iron and oxygen = 2.09/0.81 = 7.3
The same ratio confirms that these experiments clarify Law of constant proportions.
Question 6
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The following data are obtained when dinitrogen and dioxygen react together to form different compounds:

Which law of chemical combination is obeyed by the above experimental data?

A
Law of conservation of mass

B
Law of definite proportions

C
Law of multiple proportions

D
Avogadro's Law

Solution

According to the law of multiple proportions, "if two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers."
Fixing the mass of dinitrogen as 28g, masses of dioxygen combined will be 32, 64, 32 and 96 in the given figures. They are in the ratio of 1 : 2 : 1 : 3.
Question 7
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Which of the following statements illustrates the law of multiple proportions?

A
An element forms two oxides, XO and XO₂ containing 50% and 60% oxygen respectively. The ratio of masses of oxygen which combines with 1 g of element is 2:3

B
Hydrogen sulphide contains 5.89% hydrogen, water contains 11.1% hydrogen and sulphur dioxide contains 50% oxygen

C
3.47 g of BaCI₂ reacts with 2.36 g of Na₂SO₄ to give 3.88 g of BaSO₄ and 1.95 g of NaCl

D
20 mL of ammonia gives 10 volumes of N₂ and 30 volumes of H₂ at constant temperature and pressure

Solution

In XO, 50 g of element combines with 50 g of oxygen.
∴ 1 g of element combines with 1 g of oxygen.
In XO₂,40 g of element combines with 60 g of oxygen.
∴ l.g of element combines with 1.5 g of oxygen.
Thus, ratio of masses of oxygen which combines with 1 g of element is 1:1.5 or 2:3. This is in accordance with the law of multiple proportions: In (b) the law of reciprocal proportions is followed. In (c) law of conservation of mass is followed while in (d) Avogadro's law is followed.
Question 8
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Which of the following pairs illustrates the law of multiple proportions?

A
PH₃, HCl

B
PbO, PbO₂

C
H₂S, SO₂

D
CuCl₂, CuSO₄
Question 9
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Given below are few statements. Mark the statement which is not correct.

A
Gram atomic mass of an element may be defined as the mass of Avogadro's number of atoms

B
The molecular mass of a diatomic elementary gas is twice its atomic mass

C
Gay Lussac's law of chemical combination is valid for all substances

D
A pure compound has always a fixed proportion of masses of its constituents

Solution

Gay Lussac's law is true only for gaseous substances.
Question 10
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What quantity of copper oxide will react with 2.80 L of hydrogen at NTP?

A
79.5 g

B
2 g

C
9.9 g

D
22.4 g

Solution

22.4 L of H₂ = 79.5g of CuO
2.80 L of H₂= 79.5/22.4 x 2.80 = 9.9 g of CuO
Question 11
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At NTP, 1L of O₂ reacts with 3 L of carbon monoxide. What will be the volume of CO and CO₂ after the reaction?

A
1L CO₂, 1L CO

B
2L CO₂, 2L CO

C
1L CO₂, 2L CO

D
2L CO₂, 1L CO

Solution

1 vol of CO₂ reacts with 2 vol of CO
1 L of CO₂ reacts with 2 L of CO
CO left after reaction = 3 - 2 = 11
1 L of O₂ produces 2 L of CO₂.
Hence, after the reaction, CO = 1 L, CO₂ = 2 L
Question 12
1 / -0

Calcium carbonate decomposes on heating to give calcium oxide and carbon dioxide. How much volume of CO₂will be obtained by thermal decomposition of 50 g of CaCO₃?

A
1 L

B
11.2 L

C
44 L

D
22.4 L

Solution

100 g of CaCO₃ at STP gives 22.4 L of CO₂
50 g of CaCO₃ will produce 22.4/100 x 50 = 11.2 L of CO₂
Question 13
1 / -0

Chlorine gas is prepared by reaction of H₂SO₄ with MnO₂ and NaCl. What volume of CI₂ will be produced at STP if 50 g of NaCl is taken in the reaction?

A
1.915 L

B
22.4 L

C
11.2 L

D
9.57 L

Solution

(2 x 58.5 = 117 g) 22.4 L (STP)
117g of NaCl = 22.4 L of Cl₂
50 g of NaCl = 22.4/117 x 50 = 9.57 L of Cl₂ at STP
Question 14
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HCl is produced in the stomach which can be neutralised by Mg(OH)₂ in the form of milk of magnesia. How much Mg(OH)₂ is required to neutralise one mole of stomach acid?

A
29.16 g

B
34.3 g

C
58.33 g

D
68.66 g

Solution

Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O
No. of moles of Mg(OH)₂ required for 2 moles of HCl = 1
No. of moles of Mg(OH)₂ required for 1 mole of HCl = 0.5
Mass of 0.5 mol of Mg(OH)₂ = 58.33 x 0.5 = 29.16 g
Question 15
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Iron can be obtained by reduction, of iron oxide (FC₃O₄) with CO according to the reaction:
Fe₃O₄ + 4CO → 3Fe + 4CO₂
How many kg of Fe₃O₄ should be heated with CO to get 3 kg of iron?

A
8.12 kg

B
4.14 kg

C
6.94 kg

D
16.8 kg

Solution

3 moles of Fe is produced from 1 mole of Fe₃O₄
168 g of Fe is producedfrom 232 g of Fe₃O₄.
3 kg of Fe will be produced from 232/168 x 3000 g
= 4142.8 g.or 4.14 kg of Fe₃O₄