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Chemistry Test - 24

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Chemistry Test - 24
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Weekly Quiz Competition
  • Question 1
    1 / -0

    H2O2 is always stored in black bottles because:

    Solution

    On prolonged standing, hydrogen peroxide undergoes auto oxidation or disproportionation. 2H2O2→2H2O+O2 Hence, hydrogen peroxide is always stored in black bottles which cuts off the light and suppresses the auto oxidation.
    Hence, the correct option is (C)

  • Question 2
    1 / -0

    From the following statements regarding H2O2, choose the incorrect statement?

    Solution
    (A) Hydrogen peroxide can act as oxidizing as well as reducing agent. For example, in acidic medium, it oxidizes ferrous ions to ferric ions. \(2 F e^{2+}+H_{2} O_{2}+2 H^{+} \rightarrow 2 F e^{3+}+2 H_{2} O\)
    In acidic medium, hydrogen peroxide reduces HOCl to chloride ion. \(H O C l+H_{2} O_{2} \rightarrow H_{3} O^{+}+C l^{-}+H_{2} O\)
    Thus, the option A is incorrect.
    (B) It decomposes on exposure to light to form water and oxygen. \(2 H_{2} O-2 \rightleftharpoons 2 H_{2} O+O_{2}\)
    Thus, the option (B) is correct.
    (C) It has to be stored in plastic or wax, lined glass bottles in dark to prevent its decomposition. Thus, the option (C) is correct.
    (D) It has to be kept away from dust as it decomposes in presence of dust. Thus, the option (D) is correct.
    Hence, the correct option is (A)
  • Question 3
    1 / -0

    Which of the following combination will produce H2 gas?

    Solution
    Zn metal and NaOH(aq) will produce hydrogen gas. \(Z n+2 N a O H \rightarrow N a_{2} Z n O_{2}+H_{2} \uparrow\)
    Gold react with sodium cyanide, oxygen and water, but no hydrogen gas is obtained. \(4 A u+8 N a C N+O_{2}+2 H_{2} O \rightarrow 4 N a\left[A u(C N)_{2}\right]+4 N a O H\)
    Cu metal reacts with conc. nitric acid but no hydrgen gas is obtained. \(C u+4 H N O_{3} \rightarrow C u\left(N O_{3}\right)_{2}+2 H_{2} O+2 N O_{2} \uparrow\)
    Cu metal reacts with conc. nitric acid but no hydrgen gas is obtained. \(F e+6 H N O_{3} \rightarrow F e\left(N O_{3}\right)_{3}+3 H_{2} O+3 N O_{2} \uparrow\)
    Hence, the correct option is (D)
  • Question 4
    1 / -0

    Which of the following carbides give acetylene on hydrolysis ?

    Solution
    The hydrolysis of \(B e_{2} C\) gives methane. The hydrolysis of \(C a_{2} C\) and \(M g_{2} C\) gves acetylene. Whereas the hydrolysis of \(M g_{2} C_{3}\) gives allylene.
    Hence, the correct option is (A)
  • Question 5
    1 / -0

    Which physical property of hydrogen gas is wrong ?

    Solution

    Hydrogen is a highly inflammable gas. This is because it burns in air to give water. The reaction is as follows:

    H2+O2→2H2O
    Hence, the correct option is (D)

  • Question 6
    1 / -0

    Which of the following methods is used for the removal of temporary hardness of water?

    Solution

    In Clark's process, slaked lime, \(Ca ( OH )_{2}\) is added to temporary hard water. Insoluble calcium carbonate precipitate out and no longer produce hardness. Clark's process involves the addition of a controlled quantity of slaked lime (calcium hydroxide)
    \begin{equation*}
    \begin{array}{c}
    Ca \left( HCO _{3}\right)_{2}( aq )+ Ca ( OH )_{2}( aq ) \rightarrow 2 CaCO _{3}( s )+2 H _{2} O ( l ) \\
    Mg \left( HCO _{3}\right)_{2}( aq )+ Ca ( OH )_{2}( aq ) \rightarrow CaCO _{3}( s )+ MgCO _{3}( s )+2 H 2 O ( l )
    \end{array}
    \end{equation*}
    Slaked lime is itself a source of calcium ions (and hence hardness) so care must be taken to avoid adding an excess. Hence, the correct option is (D)
  • Question 7
    1 / -0

    The product(s) formed when H2O2 reacts with disodium hydrogen phosphate is:

    Solution
    \(N a_{2} H P O_{4}+H_{2} O_{2} \rightarrow N a_{2} H P O_{4} \cdot H_{2} O_{2}\)
    The product formed when \(H_{2} O_{2}\) reacts with disodium hydrogen phosphate is \(N a_{2} H P O_{4} \cdot H_{2} O_{2}\)
    Hence, the correct option is (B)
  • Question 8
    1 / -0

    With increase in number of carbon atoms in alkanes, heat of combustion:

    Solution

    With the increase in a number of carbon atoms in alkanes, the heat of combustion increases. This is because, with increase in the number of carbon atoms, the number of binds broken/formed increases due to which the heat of combustion increases. Thus, the heat of combustion of methane, ethane and butane are −80.4kJ/mol, −1580.0kJ/mol and −2875.84kJ/mol respectively.
    Hence, the correct option is (A)

  • Question 9
    1 / -0

    Acidified solution of chromic acid on treatment with H2O2 yields:

    Solution

    K2Cr2O7+H2SO4→K2SO4+H2Cr2O7

    H2Cr2O7+4H2O2→2CrO5+5H2O
    Hence, the correct option is (C)

  • Question 10
    1 / -0

    Ortho-hydrogen and para-hydrogen resembles in which of the following property?

    Solution

    Ortho and para hydrogen differ in thermal conductivity, magnetic property, heat capacity and boiling point. However, they resemble in chemical properties as their electronic configuration is the same.
    Hence, the correct option is (C)

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