1. The system which gives the eqm constant Kc , a unit of
(concentration)^-1 is
A. H2 + I2 eqm arrow 2HI
B. H20 + CH3C02C2H5 eqm arrow C2H50H +
CH3C00H
C. 2NO2 Eqm arrow N2O4
D. CH4+H20 Eqm arrow CO+H2
I know C is the answer because i've seen it the other way
round,but why arent the others the answer too? Dont they happen
too?
2.E is in period 3.Chloride of E has a simple molecular
structure, while oxide of E has a giant ionic structure.
(This isnt a choice qn ) Can you tell me why these 2 are
correct?
A. Chloride of E dissolves in water to give an acidic soln
B. Oxide of E reacts with excess aq NaOH to form a colourless
soln
3.Which property decreases fro Na2O to SiO2 and also from SiO2
to P4O10?
A. Solubility in aq alkali
B. pH when mixed with water
(why isnt the answer A? how do i find out the pH of an ionic
compound without Ka values?hmm and solubility too)
*major headache*
Q1. All other options have equal molarity units on RHS /
numerator, and LHS / denominator.
Q2. SiCl4 undergoes hydrolysis to generate HCl, but SiO2
dissolves only in molten NaOH, not aqueous. Option B is in
error.
Q3. Option A is incorrect, because solubility decreases from
Na2O to SiO2 (due to high activation energy requried to break giant
covalent lattice) but increases from SiO2 to P4O10 (since
P4O10 is strongly acidic and reacts with alkalis to generate a
soluble salt).
For the topic on periodicity, you're required to memorize the
approximate pH of the various elements when dissolved in water,
without the need for any Ka/Kb calculations.