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General Principles and Processes of Isolation of Elements Test - 51

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General Principles and Processes of Isolation of Elements Test - 51
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Weekly Quiz Competition
  • Question 1
    1 / -0
    Which of the following statement is true?
    Solution
    All ores are minerals but all metals are not ores,It is because metals cannot be extracted from minerals in a convenient way.
    Example ,Aluminium metal is found in both minerals.Clay and bauxite .
    Aluminium metal is extracted only from bauxite in a convenient way.So bauxite is an ore of aluminium.On the other hand, it is not extracted from clay  so clay remains only as minerals not ore of aluminium.
  • Question 2
    1 / -0
    For which of the following ores froth floatation method is used for concentration ?
    Solution

  • Question 3
    1 / -0
    Malachite and azurite are used respectively are : 
    Solution
    Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. The blue of azurite is exceptionally deep and clear. Specimens tend to lighten in color over time due to weathering of the specimen surface into malachite; this is why they are found together.
    they are manily Green and blue pigment

  • Question 4
    1 / -0
    Metal used for making joints in jewellery is 
    Solution
    Metal used for making joints in jewellery is copper (Cu)
  • Question 5
    1 / -0
    Which of the following metals is sometimes found native in nature ?
    Solution
    Copper is very slowly attacked by air, moisture and $$CO_2$$ and hence sometimes occurs in native state.
  • Question 6
    1 / -0
    The method of zone refining of metals is based on the principle of:
    Solution

  • Question 7
    1 / -0
    Froth flotation method cannot be employed for the concentration of:
    Solution
    Pyrolusite $$(MnO_2)$$ is an oxide ore, while zinc blende $$(ZnS)$$, copper pyrites $$(CuFeS_2)$$ and cinnabar $$(HgS)$$ are sulphide ores. Only sulphide ores are purified by froth flotatlon.

    Hence, froth flotation method cannot be employed for the concentration of pyrolusite.

    Option B is correct.
  • Question 8
    1 / -0
    The principle of fractional crystallisation is involved in which one of the following processes?
    Solution
    Fractional crystallization is a method of refining substances based on differences in solubility. Zone refining is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal (in practice, the crystal is pulled through the heater). The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot.
    Hence, the principle of fractional crystallisation is involved in zone refining.
  • Question 9
    1 / -0
    A solution of $$Na_{2}SO_{4}$$ in water is electrolysed using inert electrodes. The products at the cathode and anode respectively, are:
    Solution
    When a solution of $$Na_2SO_4$$ in water is electrolysed then reactions take place at cathode and anode are

    At anode (oxidation):

    $$2H_2O \rightarrow O_2 + 4e^- + 4H^+ $$

    At cathode ( reduction):

    $$2H^+ + 2e^- \rightarrow H_2$$.

    So, the gas librated at cathode $$= H_2$$

    and gas librated at anode $$= O_2$$.

    Option C is correct.
  • Question 10
    1 / -0
    Which of the following statements is/are correct?
    a) In the decomposition of an oxide into oxygen and metal vapour, entropy increases.
    b) Decomposition of an oxide is an endothermic change.
    c) To make $$\Delta G^{0}$$ negative, temperature should be high enough so that $$T\Delta S^{0}> \Delta H^{0}$$.
    Solution
    Decomposition of metal oxide:

    $$MO_2\rightarrow M+O_2$$

    If we compare the reactant and product, we see that the number of products are more. Also among the product side even at room temperature, one product is gas so in this process randomness increases, i.e., entropy increases.
    This is an endothermic reaction.
     
    So, to increase free energy change, the temperature should be increased to make $$T\Delta S^{o}> \Delta H^{o}$$.

    Hence option D is correct.
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