Atoms and Molecules Test

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Atoms and Molecules Test - 30

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Weekly Quiz Competition

Question 1
1 / -0

A substance formed by the reaction of hydrogen and oxygen is called a/an:

A
element

B
compound

C
solution

D
mixture

Solution

When hydrogen and oxygen are reacted, water is formed.

$$2H_2+O_2 \rightarrow 2H_2O$$

Water is a compound and its properties are different from the properties of both hydrogen and oxygen.

Hence, option B is the correct answer.
Question 2
1 / -0

Smallest particles of matter which cannot be further divided are called:

A
molecules

B
objects

C
atoms

D
none of these

Solution

The smallest particles of matter which cannot be further divided are called atoms.
Question 3
1 / -0

Which law states that the total mass of the reactants is equal to the total mass of the products in a chemical reaction?

A
Law of constant proportions

B
Law of conservation of energy

C
Law of conservation of mass

D
Law of multiple proportions

Solution

Law of conservation of mass states that in a chemical reaction, the total mass of the product is equal to the total mass of the reactants.

For example
$$CaCO_3\rightarrow CaO+CO_2$$

The total mass of reactant $$CaCO_3$$
$$=40+12+(16\times 3)=100$$

The mass of $$CaO=40+16=56$$

Mass of $$CO_2=12+(16\times 2)=44$$

The total mass of products $$CaO+CO_2=56+44=100$$.

Hence the above example illustrates that the total mass of reactants $$=$$ total mass of products.
Question 4
1 / -0

Assertion : Formula mass (in grams) of magnesium chloride has $$12.044\times 10^{23}$$ magnesium ions. Reason : One formula mass of an ionic compound has $$6.022\times 10^{23}$$ ions of each type.

A
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

B
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

C
Assertion is correct but Reason is incorrect

D
Assertion is incorrect but Reason is correct

E
Both assertion and reason are incorrect.

Solution

Formula mass of magnesium chloride $$(MgCl_2)$$ is 1 mole of $$MgCl_2$$ which has avogadro number of magnesium ions i.e., $$6.022\times 10^{23}$$ magnesium ions. One formula mass of an ionic compound has ions equal to product number of atoms and avogadro number of each type of atoms.
Question 5
1 / -0

What is the mass (in grams) of $$3$$ moles of $$N$$ atom?

A
$$28$$ g

B
$$42$$ g

C
$$84$$ g

D
$$14$$ g

Solution

Atomic mass of $$N$$ is $$14$$ u. We know that the molar mass is numerically equal to the atomic mass but expressed in g.
Mass of one mole of $$N$$ = Molar mass = $$14$$ g
Mass of $$3$$ moles of $$N$$ $$= 14\times 3 = 42$$ g
Question 6
1 / -0

What is the mass of one atom of $$C-12$$ in grams?

A
1.992$$\displaystyle \times 10^{-23}$$ gm

B
1.989$$\displaystyle \times 10^{-23}$$ gm

C
1.892$$\displaystyle \times 10^{-23}$$ gm

D
1.965$$\displaystyle \times 10^{-23}$$ gm

Solution

Mass of $$1$$ mole = $$12\,gm$$

Mass of $$6.022 \times 10^{23}\,atom = 12\,gm$$

mass of $$1$$ atom = $$\dfrac{12}{6.023 \times 10^{23}} = 1.993 \times 10^{-23}\,gm$$
Question 7
1 / -0

A neutral atom of an element has a nucleus with a nuclear charge 13 times and mass 27 times that of hydrogen nucleus. What is the ratio of electrons to protons in its stable positively charged ion?

A
27 : 13

B
10 : 19

C
10 : 13

D
10 : 14

Solution

Let the neutral atom of the element be $$X$$.

Given, the nuclear charge of $$X$$ is 13 times that of the hydrogen nucleus.
$$\Rightarrow$$ Atomic number $$=13$$

Mass of X is 27 times that of hydrogen nucleus $$\Rightarrow $$ Mass number $$=27$$.

Since $$_{13}X^{27}, EC=2, 8, 3$$

If X forms stable positively charged ion i.e., $$X^{+3}$$ (as it has 3 valence electrons in its valence shell)

$$X^{+3}\rightarrow$$ Atomic number $$=13-3=10.$$ This implies number of electrons $$=10$$. Number of protons $$=13$$.

$$Ratio=10 : 13$$
Question 8
1 / -0

When hydrogen burns in oxygen, _________ is produced.

A
water

B
hydrogen peroxide

C
both A and B

D
none of these

Solution

When hydrogen burns in oxygen, water is produced.

The reaction is as follow:
$$2H_2 + O_2 \rightarrow 2H_2O$$
Question 9
1 / -0

The percentage by mole of $${ NO }_{ 2 }$$ in a mixture of $${ NO }_{ 2 }(g)$$ and $$NO(g)$$ having average molecular mass 34 is :

A
25%

B
20%

C
40%

D
75%

Solution

Let $$x$$ represent the percentage by mole of $${ NO }_{ 2 }$$ in the mixture.

The molecular masses of $${ NO }_{ 2 }$$ and $$NO$$ are $$46$$ g/mol and $$30$$ g/mol respectively.

The average molecular mass of the mixture is $$\dfrac {46\times x +30\times (100-x)}{100}=34 $$.

Hence, $$x= 25$$ %.
Question 10
1 / -0

Barium chloride reacts with sodium sulphate to form Barium sulphate and sodium chloride. Then, according to the law of conservation of mass:

A
the total mass of reactants, barium chloride, and sodium sulphate taken is greater than the total mass of products, barium sulphate, sodium chloride formed

B
the total mass of reactants, barium chloride, and sodium sulphate is less than the total mass of products, barium sulphate, and sodium chloride

C
the total mass of the reactants is equal to the total mass of products

D
none of the above

Solution

The law of conservation of mass states that mass can neither be created nor be destroyed, it can only change from one form to the other.
So, according to the law, the amount of reactants consumed should be equal to the amount of the products formed.
Hence option C is correct.

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Atoms and Molecules Test - 30

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Atoms and Molecules Test - 30

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SHARING IS CARING

Question 1

element

compound

solution

mixture

Solution

Question 2

molecules

objects

atoms

none of these

Solution

Question 3

Law of constant proportions

Law of conservation of energy

Law of conservation of mass

Law of multiple proportions

Solution

Question 4

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Assertion is correct but Reason is incorrect

Assertion is incorrect but Reason is correct

Both assertion and reason are incorrect.

Solution

Question 5

$$28$$ g

$$42$$ g

$$84$$ g

$$14$$ g

Solution

Question 6

1.992$$\displaystyle \times 10^{-23}$$ gm

1.989$$\displaystyle \times 10^{-23}$$ gm

1.892$$\displaystyle \times 10^{-23}$$ gm

1.965$$\displaystyle \times 10^{-23}$$ gm

Solution

Question 7

27 : 13

10 : 19

10 : 13

10 : 14

Solution

Question 8

water

hydrogen peroxide

both A and B

none of these

Solution

Question 9

25%

20%

40%

75%

Solution

Question 10

the total mass of reactants, barium chloride, and sodium sulphate taken is greater than the total mass of products, barium sulphate, sodium chloride formed

the total mass of reactants, barium chloride, and sodium sulphate is less than the total mass of products, barium sulphate, and sodium chloride

the total mass of the reactants is equal to the total mass of products

none of the above

Solution

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