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*
Originally posted by vade: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 alkaliB. 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.
Q2: Actually no error, the element should be Aluminium , aluminium oxide (giant ionic), aluminium choloride (simple molecular) due to relatively polarisability of anionic cloud
(A) Al3+ high charge density (small and highly positive charged) ... hence, will produce H3O+
(B) amphoteric, so can react with aqueous alkaline, the NaAl(OH)4 will give a colourless complex ion (colourless solution)
(Partial explanations only)
Originally posted by SBS n SMRT:Q2: Actually no error, the element should be Aluminium , aluminium oxide (giant ionic), aluminium choloride (simple molecular) due to relatively polarisability of anionic cloud
(A) Al3+ high charge density (small and highly positive charged) ... hence, will produce H3O+
(B) amphoteric, so can react with aqueous alkaline, the NaAl(OH)4 will give a colourless complex ion (colourless solution)
(Partial explanations only)
Yes, my bad. I misread "giant ionic lattice" as "giant covalent lattice". It's indeed Aluminium.