Atoms and Molecules Test

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Atoms and Molecules Test - 40

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Weekly Quiz Competition

Question 1
1 / -0

Which of these would support the idea that mass is conserved in a reaction that produces gas as a product?

A
Heating the reactants to ensure the reaction occurs in a gaseous state.

B
Subtracting the mass of the gas from the mass of the solid and liquid products.

C
Mixing the reactants and measuring their total mass.

D
Trapping the gas and measuring its mass.

Solution

As gas can escape after reaction so after its release trap the gas and finding its mass so that it will be in accordance with the law of conservation of mass.
Question 2
1 / -0

The reaction of Copper with Sulphur
Mass of $$Cu$$ before reaction: $$3.17\ g$$
Mass of $$S$$ before reaction: $$2.93\ g$$
Mass of $$CuS$$ formed: $$4.78\ g$$
Mass of unreacted $$S$$: ?

Copper $$(Cu)$$ and Sulphur $$(S)$$ were heated in a covered container. After the reaction was complete, the unreacted sulphur was removed. The table contains the results of the investigation. How much sulphur, in grams, failed to react with the copper?

A
$$1.2$$

B
$$1.25$$

C
$$1.3$$

D
$$1.32$$

Solution

According to the law of conservation of mass, “Mass can neither be created nor be destroyed but can be transformed from one form to another”. Which can be interpreted as, the mass of reactants= the mass of products.

Mass of $$Cu$$ before reaction $$+$$ mass of $$S$$ before reaction $$=$$ mass of $$CuS$$ formed $$+$$ unreacted$$ S$$
Therefore mass of unreacted $$S = 3.17\ g + 2.93\ g - 4.78\ g = 1.32\ g$$
Question 3
1 / -0

In a chemical reaction, $$100 g$$ baking soda mixture containing sodium bicarbonate and vinegar on heating gives $$43 g$$ of carbon dioxide gas. What mass of solid residue is left in food?

A
$$54\ g$$

B
$$55\ g$$

C
$$56\ g$$

D
$$57\ g$$

Solution

According to law of conservation of mass, total mass of reactants is equal to total mass of products. Here baking soda mixture on heating gives solid residue and carbon dioxide.
$$M_{\text {Baking soda mixture}} = M_{\text {solid residue}} + M_{CO_{2}}$$
or it can be written as:
$$M_{\text {solid residue}} = M_{\text {Baking soda mixture}} - M_{CO_{2}}$$ $$(Eq 1)$$
According to the question
$$M_{\text {Baking soda mixture}} = 100 g$$
$$M_{CO_{2}} = 43 g$$
Substituting the value in equation $$1$$, we get
The mass of solid residue is $$100g - 43g =57 g$$
Question 4
1 / -0

Calculate the molecular mass (u) of Phosphoric Acid ($$\displaystyle { H }_{ 3 }{ PO }_{ 4 }$$).
$$[H=1, P=31, O=16]$$

A
96

B
97

C
98

D
99

Solution

Molecular mass (u) of Phosphoric Acid ($$\displaystyle { H }_{ 3 }{ PO }_{ 4 }$$) $$= 3 \times mass \ of\ H \ atoms + mass\ of\ phosphorous\ atom + 4 \times mass\ of\ oxygen\ atom$$
$$= 3 + 31 + 64 = 98u$$
Question 5
1 / -0

Calculate the formula unit mass (u) of $$\displaystyle { CaCl }_{ 2 }$$.
[ Ca = 40 u, Cl = 35.5 u]

A
111 u

B
101 u

C
91 u

D
55 u

Solution

$$Formula\ unit\ mass = Atomic\ mass\ of\ Ca + (2\times Atomic\ mass \ of \ Cl) = 40 + (2 \times 35.5) = 40 + 71 = 111\ u$$
Question 6
1 / -0

Calculate the molecular mass of Nitric acid ($$\displaystyle { HNO }_{ 3 }$$).

A
60

B
61

C
62

D
63

Solution

molecular mass of $$\displaystyle { HNO }_{ 3 }$$ = mass of H atom + mass of nitrogen atom + 3 x mass of oxygen atom
$$= 1 + 14 + 48 = 63 u$$
Question 7
1 / -0

Calculate the molecular mass (u) of Sulphuric acid ($$\displaystyle { H }_{ 2 }{ SO }_{ 4 }$$).

A
96

B
97

C
98

D
49

Solution

Molecular mass (u) of Sulphuric acid ($$\displaystyle { H }_{ 2 }{ SO }_{ 4 }$$) = 2 x mass of H atom + mass of S atom + 4 x mass of O atom
$$= 2 \times 1 + 32 + 4 \times 16$$
$$= 98$$
Question 8
1 / -0

When $$1.375\ g$$ of cupric oxide is reduced on heating in a current of hydrogen, the weight of copper remaining $$1.098\ g$$. In another experiment, $$1.179\ g$$ of copper is dissolved in nitric acid, and the resulting copper nitrate is converted into cupric oxide by ignition. The weight of cupric oxide formed is $$1.476 \ g$$. This is in agreement with :

A
Law of definite proportion

B
Law of mass conservation

C
Law of momentum conservation

D
None of the above
Question 9
1 / -0

Calculate the molecular mass (u) of $$\displaystyle ZnO$$.
$$ [Zn = 65u, O = 16u]$$

A
$$80$$

B
$$69$$

C
$$82$$

D
$$81$$

Solution

Molecular mass of $$\displaystyle ZnO$$ = Atomic mass of zinc + atomic mass of oxygen
$$= 65u + 16u = 81u$$
Question 10
1 / -0

Which is not one of the laws of chemical combinations?

A
Law of multiple proportion

B
Law of conservation of mass

C
Law of conservation of energy

D
Law of definite proportion

Solution

The Law of conservation of energy is not one of the laws of chemical combinations.

Hence, the correct option is C.

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Re-Attempt Weekly Quiz Competition

The reaction of Copper with Sulphur
Mass of $$Cu$$ before reaction:	$$3.17\ g$$
Mass of $$S$$ before reaction:	$$2.93\ g$$
Mass of $$CuS$$ formed:	$$4.78\ g$$
Mass of unreacted $$S$$:	?

Atoms and Molecules Test - 40

Result

Atoms and Molecules Test - 40

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SHARING IS CARING

Question 1

Heating the reactants to ensure the reaction occurs in a gaseous state.

Subtracting the mass of the gas from the mass of the solid and liquid products.

Mixing the reactants and measuring their total mass.

Trapping the gas and measuring its mass.

Solution

Question 2

$$1.2$$

$$1.25$$

$$1.3$$

$$1.32$$

Solution

Question 3

$$54\ g$$

$$55\ g$$

$$56\ g$$

$$57\ g$$

Solution

Question 4

96

97

98

99

Solution

Question 5

111 u

101 u

91 u

55 u

Solution

Question 6

60

61

62

63

Solution

Question 7

96

97

98

49

Solution

Question 8

Law of definite proportion

Law of mass conservation

Law of momentum conservation

None of the above

Question 9

$$80$$

$$69$$

$$82$$

$$81$$

Solution

Question 10

Law of multiple proportion

Law of conservation of mass

Law of conservation of energy

Law of definite proportion

Solution

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