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Question 12 Marks
Wavelengths of different radiations are given below:
$
\lambda=(A) 300 nm
$
$\lambda(B)=300 \mu m$
$\lambda( C )=3 nm$
$\lambda$ (D) $=30 \stackrel{\circ}{A}$
Arrange these radiations in the increasing order of their energies.
Answer
$
\begin{aligned}
& \lambda(A)=300 nm=300 \times 10^{-9} m \\
& \lambda(B)=300 \mu m=300 \times 10^{-6} m
\end{aligned}
$
$
\begin{aligned}
& \lambda(C)=3 nm=3 \times 10^{-9} m \\
& \lambda(D)=30 \stackrel{\circ}{A}=3 \times 10^{-9} m
\end{aligned}
$
We know that, $E \propto \frac{1}{\lambda}$.
Since, increasing order of wavelength is given as, $300 \mu m<300 nm<3 nm<30 \stackrel{o}{A}$
Therefore, $\lambda(B)<(A)<\lambda(C)=\lambda(D)$
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Question 22 Marks
Suggest a route to prepare ethyl hydrogensulphate $\left( CH _3- H _2- OSO _2- OH \right)$ starting from ethanol $\left( C _2 H _5 OH \right)$.
Answer
Ethanol when treated with sulphuric acid at around $140^{\circ} C$ gives hydrogen sulphate. The reaction takes place as follows.
Image
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Question 32 Marks
Explain why the system are not aromatic.
Image
Answer
For the given compound, the number of $\pi$-electrons is 8 .
By Huckel's rule,
$
\begin{aligned}
& \Rightarrow 4 n+2=8 \\
& \Rightarrow 4 n=6 \\
& \Rightarrow n=3 / 2
\end{aligned}
$
This is not true for the given compound as it is a fraction. Hence, it is not aromatic in nature.
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Question 42 Marks
Determine the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are 69.9 and 30.1 respectively.
Answer
The mass per cent of iron $( Fe )=69.9 \%$ ( given )
The mass per cent of oxygen $(O)=30.1 \%$, ( given)
Number of moles of iron present in the oxide $=[69.9 / 55.85]$
Number of moles of oxygen present in the oxide $=[30.1 / 16]$
The ratio of iron to oxygen in the oxide, $=1.25: 1.88$
$
\begin{aligned}
& \text { or, }=(1.25 / 1.25):(1.88 / 1.25) \\
& =1: 1.5
\end{aligned}
$
So, a whole number ratio
$
=2: 3
$
hence, the empirical formula of the oxide is $Fe _2 O _3$
The empirical formula mass of $Fe _2 O _3=2 \times 55.85+3 \times 16.00$
$
\begin{aligned}
& =159.7 g mol^{-1} \\
& n=\frac{Molar \text { mass }}{\text { Empirical formula mass }} \\
& n=159.69 g / 159.7 g=0.9999 \\
& =1 \text { (approx.) }
\end{aligned}
$
The molecular formula of a compound is obtained by multiplying the empirical formula with this positive integer ( n ) Thus, as per the empirical formula $\left( Fe _2 O _3\right)$ of the given oxide, $n =1$.
Hence, the molecular formula is same as empirical formula, $Fe _2 O _3$
The molecular formula of the oxide is $Fe _2 O _3$
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Question 52 Marks
What would be IUPAC names and symbols for elements with atomic numbers 122, 127, 135, 149 and 150?
Answer
The roots 2, 7, 5, 9 and 0 are referred as bi, hept, pent, enn and nil respectively. Therefore, their names and symbol are

Z(Atomic number)NameSymbol
122UnbibiumUbb
127UnbiseptiumUbs
135UntripentiumUtp
149UnquadenniumUqe
150UnpentniliumUpn
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Question 62 Marks
Mention the general characteristics of equilibria involving physical processes.
Answer
The general characteristics involving physical equilibria are
a. Equilibrium is possible only in a closed system at a given temperature.
b. Both the opposing processes occur at the same rate and there is a dynamic but stable condition.
c. All measurable properties of the system remain constant.
d. The magnitude of such quantities at any stage indicates the extent to which the physical process has proceeded before reaching equilibrium.
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