Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Combustion of $16g$ of methane gives $18g$ of water.
Reason $(R)$ : In the combustion of methane, water is one of the products.

A
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
B
$A$ is true but $R$ is false.
✓
$A$ is false but $R$ is true.
D
Both $A$ and $R$ are false.

Answer

Correct option: C.

$A$ is false but $R$ is true.

$\mathrm{CH}_4(\mathrm{g})+2 \mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{CO}_2(\mathrm{g})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{g})$
$16 \mathrm{g}^2$ of $\mathrm{CH}_4$ on complete combustion will give $36 g$ of water

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MCQ 21 Mark

Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : Significant figures for $0.200$ is $3$ where as for $200$ it is $1.$
Reason $(R)$ : Zero at the end or right of a number are significant provided they are not on the right side of the decimal point.

A
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
B
$A$ is true but $R$ is false.
✓
$A$ is false but $R$ is true.
D
Both $A$ and $R$ are false.

Answer

Correct option: C.

$A$ is false but $R$ is true.

Significant figures for $0.200 = 3$
Significant figure for $200 = 1$
Zeros at the end of a number without decimal $-$ point, may or may not be significant depending on the accuracy of measurement.

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MCQ 31 Mark

Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : The empirical mass of ethene is half of its molecular mass.
Reason $(R)$ : The empirical formula represents the simplest whole number ratio of various atoms present in a compound.

✓
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
B
$A$ is true but $R$ is false.
C
$A$ is false but $R$ is true.
D
Both $A$ and $R$ are false.

Answer

Correct option: A.

Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$

Molecular formula $= n\ \times\ ($emprirical formula$)$
$\text{n}=\frac{\text{Molecular mass}}{\text{Empirical formula mass}}$
Empirical formula of ethene $= \mathrm{CH}_2$
Empirical formula mass of ethene $= 14$ amu
$=\frac{1}{2}\times$ molecular mass of ethwne
Emprical formula show that ethene has $(C : H) 1 : 2$

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MCQ 41 Mark

Note : In the following questions a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below each question.
Assertion $(A)$ : One atomic mass unit is defined as one twelfth of the mass of one carbon $-12$ atom.
Reason $(R)$ : Carbon $-12$ isotope is the most abundunt isotope of carbon and has been chosen as standard.

A
Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
✓
$A$ is true but $R$ is false.
C
$A$ is false but $R$ is true.
D
Both $A$ and $R$ are false.

Answer

Correct option: B.

$A$ is true but $R$ is false.

$1\text{a}\ \text{mu}=\frac{1}{12}\times\text{Mass of one}\text{C}^{12}\text{Atom}\Big|\text{C}^{12}$
Isotope is considered as standard for defining the atomic and molecular mass.

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Chemistry Assertion (A) & Reason (B) MCQ

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