• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

P1 MCQ's preparation thread for chemistry ONLY!!!!

Messages
325
Reaction score
215
Points
53
in question no 9,at equilibrium moles of p will be (2-x),R will be (x).adding them togather & putting them equal to (2+x).still confused!!

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_12.pdf .kindly also tell these qusetions.2(why not B),10,33.thanks alot!!!

2. Number of electrons = 10 (it's a negative ion) which also = the number of neutrons.
10. In symmetrical molecules, dipoles cancel out.
33. 1 is true because H2SO4 will dissociate lots since it's a strong acid. For 2, you'll have to check and see where the SO42- ion comes from. It comes from the dissociation of HSO4- ions, which are weak, so they don't dissociate much. Hence obviously 3 is wrong.
 
Messages
325
Reaction score
215
Points
53

3. Use pV=nRT.
14. The moles of metal nitrate and metal oxide are the same (you can find that by constructing a balanced equation for he decomposition of a Group II metal nitrate). The mass of metal nitrate is given; 3-1.53=mass of metal oxide. n=mass/Mr. mass/Mr of metal oxide = mass/Mr of metal nitrate. Cross multiply and find x in each Mr.
 
Messages
887
Reaction score
466
Points
73

for Q3 use the formula PV=nRT
(95*10^3)*(4.32*10^-5)=n*8.13*(40+273)
n is the number of moles mr of NH3 is 17
n/17 u get the mass

for Q14
for any group 2 metal nitrate decomposition equation is


2M(NO3)2 yields 2MO+4NO2+O2

let the molecular mass of metal nitrate be X
as the mass is conserved so mass of the oxide is 3-1.53 as oxide is solid.
number of moles of nitrate and oxide are the same
3/X number of moles of nitrate
X is mr of that metal nitrate here comes the tricky part
u want to find the mr of metal oxide
this will give u mass of 2*mr as there are 2 moles of oxide
2X-(32+4(14+32)
we want mr so divide it by 2
(3/X)=1.47/(X-108)
3*(X-108)=1.47X
1.53X=324
X=211.76
211.8-108
103.8-16
87.8 only strontium fits in so it is correct

for Q15 u know down the group halogens become reducing agents
iodine is a reducing agent this means it will reduce the sulfuric acid
hydrogen has +2 charge in hydrogen sulfide water and sulfuric acid no change in hydrogen's oxidation number
oxygen is oxidized only sulfur is reduced
it has charge of -2 in H2S it has a charge of +6 in sulfuric acid the change is 8 right
 
Messages
325
Reaction score
215
Points
53

9. Since the reaction is reversed, the Kc will become the reciprocal of the forward reaction. So 1/2. Since all the moles are divided by two, the new Kc will be the root of 1/2.
10. Study the graph. L shows the number of molecules with the least energy, M with the average energies and N with the highest energies. What'll happen to the numbers of molecules with the least energy when the temperature increases?
12. AlCl3 is ionic; Al2Cl6 is covalent. MgCl2 is very slightly acidic in solution.
13. Draw the compound.
14. Bonds broken - endothermic. Bonds made - exothermic.
16. Draw a Hess cycle.
18. An ammonium compound will release ammonia upon reaction with an alkali.
20. Draw both compounds.
22. A carbocation is a positive ion.
26. Tertiary alcohols resist oxidation.
34. Use Le Chatelier's principle.
37. Bond energy doesn't have anything to do with the reaction actually taking place, only with how much energy is required for bonds to be made or broken.
39. ?
40. Esters get hydrolysed by acids.
 
Messages
69
Reaction score
32
Points
18
Why can we not oxidise this compound? It has OH group so it should be oxidised which is written in 2. Summer 2005, Q39.
Question.JPG
 
Messages
134
Reaction score
117
Points
28
Why can we not oxidise this compound? It has OH group so it should be oxidised which is written in 2. Summer 2005, Q39.
View attachment 28630

Primary alcohols are oxidised to aldehyde and then carboxylic acid. if you make a displayed formula of the compound, you will see that the OH groups represent a secondary alcohol. Since secondary alcohols are oxidised to ketones and not carboxylic acids, 2 is a wrong option.
 
Top