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Chemistry Test-24

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Chemistry Test-24
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  • Question 1
    4 / -1

    For the reaction \(A(g)+2 B(g) \rightleftharpoons C(g)+D(g) ; K_{C}=10^{12}\). If the initial moles of \(A, B, C\) and \(D\) in a one liter vessel are \(0.5,1,0.5\) and \(3.5\) moles respectively. What is the equilibrium concentration of \(B\)?

    Solution

    The equilibrium reaction is \(A ( g )+2 B ( g ) \rightleftharpoons C ( g )+ D ( g )\).

    The initial moles of \(A , B , C\) and \(D\) are \(0.5,1,0.5\) and \(3.5\) moles respectively.

    The equilibrium moles of \(A , B , C\) and \(D\) are \(0.5- x , 1-2 x , 0.5+ x\) and \(3.5+ x\) moles respectively.

    The expression for the equilibrium constant is \(K _{ c }=\frac{[ C ][ D ]}{[ A ][ B ]^{2}}\).

    Substitute values in the above expression.

    \(K _{ c }=\frac{(0.5+ x )(3.5+ x )}{(0.5- x )(1-2 x )^{2}}\)

    So, \(x=0.4999\) and \([B]=(1-2 x)=2 \times 10^{-4}\).

  • Question 2
    4 / -1

    Which of the following statements regarding adsorption is not correct?

    Solution

    The activation energy in chemisorption is larger than that in physisorption. Consequently, an increase in temperature initially increases the rate of chemisorption as the heat supplied provides the activation energy for the process.

  • Question 3
    4 / -1

    What is the main factor responsible for weak acidic nature of B-F bonds in BF3?

    Solution

    \(p \pi-p \pi\) back-bonding is the main factor responsible for the weak acidic nature of B-F bonds in BF3.

  • Question 4
    4 / -1

    If a nucleus of atomic mass number \(240\) breaks into two smaller nuclei then the nucleons of the new nuclei get in the process.

    Solution

    The binding energy of a particle can be defined as the minimum energy required to remove nucleons (Proton or neutron) to an infinite distance from the nucleus. It can be expressed as:

    \(\Delta E=\Delta m c^{2}\)

    Whereas Binding energy per nucleus, \(E_{b n}=\frac{\Delta E}{A}\)

    From the above, we can see that, as atom becomes heavier Binding energy increases. i.e., it means that it takes more energy to remove a single nucleus as atomic mass increase.

    So, we can say that after fission when a heavier nucleus of atomic mass\(240\) breaks into lighter nucleus the new atom will have more binding energy and it will be more tightly bound and energy would be released in a form of heat and radiation.

  • Question 5
    4 / -1

    Inhaling _________ in large amounts can cause pulmonary edema.

    Solution

    Inhaling of nitrogen oxides by humans results in pulmonary edema and hemorrhage. Several sensitive plants get adversely affected by NOx even at the concentration of 1 ppm for a day or 0.35 ppm for a few months. The affected plants start shedding their leaves and fruit. Nitrogen oxides cause fading of textile dyes and deterioration of cotton and nylon fabrics.

  • Question 6
    4 / -1

    Which of the following statements regarding adsorption is not true?

    Solution

    During adsorption, there occurs an increase in entropy of the systemregarding adsorption is not true.

  • Question 7
    4 / -1

    The value of n in the molecular formula BenAl2Si6O18 is:

    Solution

    Given,

    Molecular formula =BenAl2Si6O18

    The oxidation states of each element of given molecular formula:

    Be = +2

    Al = +3

    Si = +4

    O = -2

    (2n) + (3 × 2) + (4 + 6) + (−2 × 18) = 0

    2n + 30 − 36 = 0

    2n = 6

    n = 3

  • Question 8
    4 / -1

    Which of the following is a secondary amine?

    Solution

    Diphenyl amine is aromatic secondary amine. N atom is attached to two aryl groups and one H atom. Aniline is aromatic primary amine. Sec. butyl amine and tert. butyl amine are aliphatic primary amines.

  • Question 9
    4 / -1

    \(E_n=-\frac{313.6}{n^2}\), if the value of \(E_i=-40\) to which value 'n' corresponds?

    Solution

    Given :- \(E _n=\frac{-313.6}{n^2}\)

    To calculate:- The value of \(n\) if the value of \(E _i=\) \(-40 k c a l\) mol \(^{-1}\)

    \(E_i=-40\)

    By the Nernst equation,

    \(E_i = E_n\)

    Therefore,

    \(-40=\frac{-313.6}{n^2}\)

    \(n^2=\frac{313.6}{40}\)

    \(n^2=7.84\)

    \(n= \sqrt 7.84\)

    \(n=2.8 \approx 3\)

  • Question 10
    4 / -1

    \(200 MeV\) of energy may be obtained per fission of \(U^{235}\). A reactor is generating \(1000 kW\) of power, the rate of nuclear fission in the reactor is?

    Solution

    Energy is \(200 Mev\), converting into \(eV\) we get, \(200 \times 10^{6} ev\). But the standard SI unit is Joules, thus converting into \(200 \times 10^{6} \times 1.6 \times 10^{-19} J\). Also, the power is \(1000 kW\) converting it into watts we get \(1000 \times 1000=10^{6} W\)

    We know power is given by \(P=\frac{n E}{t}\), putting the value we get,

    \(\Rightarrow P=\frac{n E}{t}\)

    \(\Rightarrow \frac{P}{E}=\frac{n}{t}\)

    \(\Rightarrow \frac{n}{t}=\frac{10^{6}}{200 \times 10^{6} \times 1.6 \times 10^{-19}}\)

    \(\therefore \frac{n}{t}=3.125 \times 10^{16}\)

    So, the rate of nuclear fission comes out to be \(3.125 \times 10^{16}\).

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