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Chemistry Test - 17

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Chemistry Test - 17
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Weekly Quiz Competition
  • Question 1
    4 / -1

    Which of the following statements is not true?

    Solution

    Proteins are essential nutrients for the human body.[1] They are one of the building blocks of body tissue, and can also serve as a fuel source. Although your body can manufacture many of the 20 amino acids necessary to make proteins, it can't make them all. Those your body can't produce, called the essential amino acids, must come from the foods you eat.

  • Question 2
    4 / -1

    NH3 gas at 1 atm and HCl gas at P atm are allowed to effuse at room temperature through identical pinholes from opposite ends of a glass tube of 1 m length and uniform cross-section. NH4Cl is first formed at a distance of 60 cm from the end, through which HCl gas is sent into the tube. What is the value of P?

    Solution

    The pressures of the gases are different, but their temperature is constant. Therefore, the rate of effusion of the gas molecules will be directly proportional to the square root of the pressure and is inversely proportional to the square root of the molecular mass according to Graham`s law.

    Thus, combining the two, we have

    \(u \propto \sqrt{\frac{P}{M}}\) or \(r=k \sqrt{\frac{P}{M}},\) where \(k\) is constant of proportionality
    Now, \(\mathrm{r}_{\mathrm{HCl}}=\mathrm{k} \times \sqrt{\frac{\mathrm{P}(\mathrm{atm})}{36.5}}, \mathrm{r}\left(\mathrm{NH}_{3}\right)=\mathrm{k} \times \sqrt{\frac{1(\mathrm{atm} .)}{17}}\)
    The ratio of the two rates is equal to the ratio of the distance travelled by the two gases.
    i.e.
    \(\frac{\mathrm{rHCl}}{\mathrm{rNH}_{2}}=\frac{60 \mathrm{cm}}{40 \mathrm{cm}}\)
    Or, \(\frac{k \sqrt{P / 36.5}}{k \sqrt{1 / 17}}=\frac{60}{40}\) or, \(\sqrt{\frac{P \times 17}{36.5 \times 1}}=\frac{60}{40}\)
    Or, \(P=\frac{60 \times 60 \times 36.5}{40 \times 40 \times 17}=4.83\) atm
  • Question 3
    4 / -1

    A colloidal phase in which gas bubbles are dispersed in a liquid phase is known as

    Solution

    A foam is a colloidal system in which gas bubbles are dispersed in a liquid or solid. Although the diameters of the bubbles usually exceed 104Å, the distance between the bubbles is usually less than 104Å, so foam is classified as colloidal system.

  • Question 4
    4 / -1

    Dalton's law of partial pressure is applicable to which of the following systems?

    Solution
    Dalton's law of partial pressure is applicable to the mixtures of non-reacting gases. Nitrogen and hydrogen do not react under ordinary conditions and form a mixture and will obey Dalton's law of partial pressures, i.e. \(P_{T}=P_{H_{2}}+P_{N_{2}}\) However under high temperature and pressure conditions and in the presence of a catalyst, the react
    to form \(\mathrm{NH}_{3}\).
    All the other options are of gases that react with each other. \(N H_{3}+H C l \rightarrow N H_{4} C l\)
    \(2 N O+O_{2} \rightarrow 2 N O_{2}\)
    \(\mathrm{CO}+3 \mathrm{H}_{2} \rightarrow \mathrm{CH}_{3} \mathrm{OH}+\mathrm{H}_{2} \mathrm{O}\)
  • Question 5
    4 / -1

    The standard Gibb's free energy of the following reaction at 25oC is 38484 J.

    PCl5 (g) PCl3 (g) + Cl2 (g)

    The value of equilibrium constant is

    Solution
    Use \(\Delta G=-2.303\) RT \(\log \mathrm{K}\)
    \(\log \mathrm{K}=\frac{-\Delta G}{2.303 \times R \times T}\)
    \(\log \mathrm{K}=-\frac{38484}{2.303 \times 8.314 \times 298}\)
    \(\log \mathrm{K}=-6.75 \mathrm{K}=\operatorname{antilog}(-6.75)=1.8 \times 10^{-7}\)
  • Question 6
    4 / -1

    Directions: The following question has four choices out of which ONLY ONE is correct.

    Which of the following statements is not correct?

    Solution

    Physical adsorption can be reversed by increasing the temperature. So, it is a reversible process.

  • Question 7
    4 / -1

    Which of the following statements is incorrect?

    Solution

    BCC structure of metals is shown below. The metal atom at the centre of the body is surrounded by 8 metal atoms that are at the corners of the cube. Hence, option (1) is incorrect.

    The crystal structure of CsCl forms a major structural type where each cesium ion is coordinated by 8 chlorine ions as shown below.

    Thus, option (2) is correct.

    Every unit cell shares some of its atoms/ions with other unit cells. So, option (3) is also correct.

    In unit cell of NaCl, the Cl- ions are arranged at the corners as well as at the centres of the faces, while the Na+ ions occupy the centres of the edges along with a position at the body centre.

    The Na+ and Cl- ions are touching each other along the edge of the unit cell.

    So, edge length =2rNa++ 2rcl-

    = (2 x 95) + (2 x 181) = 552 pm

    Therefore, option (4) is also correct.

  • Question 8
    4 / -1

    If 150 kJ of energy is needed for a man to walk a distance of 1 km, then how much glucose does one have to consume to walk a distance of 5 km, provided that only 30% of energy is available for muscular work? (The enthalpy of combustion of glucose is 3000 kJ mol-1.)

    Solution
    150 kJ of energy required for muscular work to walk a distance of one km. (Given) \(750 \mathrm{kJ}\) energy required for work to walk of 5 \(\mathrm{km}\) distance enthalpy of combstion is \(3000 \mathrm{kJ} \mathrm{mol}^{-1}\)
    Glucose provide \(30 \%\) energy of its mass. Molecular wt. of glucose \(=180\)
    Weight of glucose required for work to \(5 \mathrm{km}\) (750 k energy)
    \[
    \begin{array}{l}
    =\frac{180}{3000} \times 750 \times \frac{100}{30} \\
    =150 \mathrm{g}
    \end{array}
    \]
  • Question 9
    4 / -1

    Directions: The following question is based on the paragraph given below:

    Chemical reactions involve interaction of atoms and molecules. A large number of atoms / molecules (approximately 6.023 ×1023 ) are present in a few grams of any chemical compound varying with their atomic /molecular masses. To handle such large numbers conveniently, the mole concept was introduced.

    This concept has implications in diverse areas such as analytical chemistry, biochemistry electrochemistry and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear understanding of the mole concept. A 4.0 molar aqueous solution NaCl is prepared and 500 mL of this solution is electrolysed. This leads to the evolution of chlorine gas at one of the electrodes (Atomic mass : Na = 23, Hg = 200;1 Faraday = 96500 coulombs).

    If the cathode is a Hg electrode, the maximum weight (g) of amalgam formed from this solution is

    Solution

    In presence of Hg cathode sodium ion will discharge in place of hydrogen gas due to over voltage in the form of amalgams.

    Weight of amalgam = 2 × (23 + 200) = 446 g

  • Question 10
    4 / -1

    Consider the following vapour pressure - mole fraction graph. SP (Total vapour pressure of the resultant solution) is equal to

    Solution

    \(\mathrm{sP}=\) total pressure of resultant solution at \(\mathrm{x}_{\mathrm{B}}=0.8\)

    \(P_{t}=p_{1}+p_{2}\)

    \(\mathrm{SP}=\mathrm{SR}+\mathrm{SQ}\)

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