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    I'm struggling a bit with these questions

    1) The use of an indicator is not appropriate in titrations involving:-
    A) HCL solution and methylamine solution
    B) Nitric acid solution and potassium hydroxide solution
    C) Methanoic acid solution and ammonia solution
    D) Propanoic acid solution and sodium hydroxide solution

    The answer is C, but why? I was able to rule out B and D

    2) Which of the following cannot be described as an enthalpy of formation?
    A) Si(s) + 4Cl(g) --> SiCl4(l)
    B) Mg(s) + 1/2 O2(g) --> MgO(s)
    C) C(s) + 2H2(g) + 1/2 O2(g) --> CH2OH(l)
    D) 2C(s) + 3H2(g) --> C2H6(g)

    The answer is A, but silicon and chlorine are both in their standard states and 1 mole of SiCl4 is produced

    3) 0.02 moles of the salt Pt(NH3)xCl2 required 20cm3 of 4mol/l nitric acid to react completely with the NH3 ligands.
    The value of x is
    A) 2
    B) 4
    C) 6
    D) 8

    The answer is B, but I'm not sure how to calculate 'x'
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    For 1) the answer is C as it is a weak acid weak base titration. The titration cure would have no clear vertical part.

    For 2) note that you have 4Cl not 2Cl2
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    (Original post by thatawesomekid)
    For 1) the answer is C as it is a weak acid weak base titration. The titration cure would have no clear vertical part.

    For 2) note that you have 4Cl not 2Cl2
    Thanks!! It makes sense now
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    (Original post by RobynM27)
    Thanks!! It makes sense now
    No worries, sorry I can't help with the last question
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    (Original post by RobynM27)
    C) C(s) + 2H2(g) + 1/2 O2(g) --> CH2OH(l)
    [Pedant]CH3OH[/pedant]

    3) 0.02 moles of the salt Pt(NH3)xCl2 required 20cm3 of 4mol/l nitric acid to react completely with the NH3 ligands.
    The value of x is
    A) 2
    B) 4
    C) 6
    D) 8

    The answer is B, but I'm not sure how to calculate 'x'
    You are adding 20/1000 x 4 = 0.08 mol of HNO3

    0.08 mol of HNO3 will react with 0.08 mol of NH3

    You have 0.02 mol of Pt(NH3)xCl2

    Each mol of Pt(NH3)xCl2 must contain 4 mol of NH3

    Bingo.
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    Now that you know x = 4, (correctly worked out by Pigster), I would double-check with balanced equation:

    Pt(NH3)4 + 4HNO3 gives Pt(NO3)4 + 4NH4

    (Almost?) always, f you cannot balance an equation, something is incorrect!
 
 
 
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