Chemistry MCQ thread...

[Iadmireblue]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
please help me with question 2 and 6..

For question 6,find out how many grams of N there are in 1g of fertiliser,this would be 15/100 which is 0.15 g of nitrogen in a gram of fertiliser.So in 14 g there would be 0.15*14 =2.1 grams.
Concentration=Moles/volume.
Now find moles = mass/MR =2.1/13=0.15
then conc=0.15/5 which gives 0.03moldm^-3

 

[Kumkum]

For question 6,find out how many grams of N there are in 1g of fertiliser,this would be 15/100 which is 0.15 g of nitrogen in a gram of fertiliser.So in 14 g there would be 0.15*14 =2.1 grams.
Concentration=Moles/volume.
Now find moles = mass/MR =2.1/13=0.15
then conc=0.15/5 which gives 0.03moldm^-3

thnx! can you help me with question 6...the one you answered is question 2

 

[InnocentAngel]

Please help quick. 3hrs left b4 xms

 

[InnocentAngel]

Please help quick. 3hrs left b4 xms View attachment 18651

lol no the ans is B itself lol

 

[ZohaibAsad]

Please help quick. 3hrs left b4 xms View attachment 18651

Year and paper number ? It should be 91.3, very rarely mark schemes have the wrong answer posted so I'll double check it

 

[ZohaibAsad]

lol no the ans is B itself lol

Exam pressure exam pressure ! Have a red bull

 

[InnocentAngel]

Exam pressure exam pressure ! Have a red bull

Hahaha yeah x'D

 

[athaan]

Oh my, I'd say the paper was quite hard!
I even didn't finish on time

 

[Amy Bloom]

GT?

 

[balay]

does an alkene react with acidified pottasium dichromate??....can sme1 please answer????

 

[iKhaled]

does an alkene react with acidified pottasium dichromate??....can sme1 please answer????

nope, it would react with potassium manganate not potassium dichromate

 

[athaan]

aren't we not supposed to discuss the questions before 24h of the test...?

 

[iKhaled]

aren't we not supposed to discuss the questions before 24h of the test...?

this is not a discussion..we r talking generally about chemistry. i didn't even do the exam today but i just answered his "general chemistry question" sorry if this was part of the exam and i have discussed it..i didn't even know u guys had an exam today

 

[magnesium]

Two moles of compound P were placed in a vessel. The compound P was partly decomposed by
heating. A dynamic equilibrium between chemicals P, Q and R was established.
At equilibrium, x mol of R were present and the total number of moles present was (2 + x).
What is the equation for this equilibrium?
A P ---->< 2Q + R
B 2P ----><2Q + R
C 2P----->< Q + R
D 2P ------>< Q + 2R
----->< this sign represents revesible reaction................CAN SOMEONE HELP!

 

[magnesium]

How many isomeric esters have the molecular formula C4H8O2?
A 2 B 3 C 4 D 5
HELP!!!

 

[magnesium]

Use of the Data Booklet is relevant to this question.
A sample of ethyl propanoate is hydrolysed by heating under reflux with aqueous sodium
hydroxide. The two organic products of the hydrolysis are separated, purified and weighed.
Out of the total mass of products obtained, what is the percentage by mass of each product?
A 32.4% and 67.6%
B 38.3% and 61.7%
C 42.3% and 57.7%
D 50.0% and 50.0%

 

[aalmuhannadi]

Two moles of compound P were placed in a vessel. The compound P was partly decomposed by
heating. A dynamic equilibrium between chemicals P, Q and R was established.
At equilibrium, x mol of R were present and the total number of moles present was (2 + x).
What is the equation for this equilibrium?
A P ---->< 2Q + R
B 2P ----><2Q + R
C 2P----->< Q + R
D 2P ------>< Q + 2R
----->< this sign represents revesible reaction................CAN SOMEONE HELP!

A: initial: 2 moles of P
equilibrium: x moles of R, therefore there must be 2x moles of Q (as the ratio of Q to R is 2:1). P will be 2-x moles (we subtract moles of R from moles of P since they are the same in equilibrium)
Add them up: x + 2x + 2 - x = 2x + 2 so A is incorrect

B: initial: 2 moles of P
equilibrium: x moles of R, therefore there must be 2x moles of Q (as the ratio of Q to R is still 2:1). P will be 2-2x moles (we subtract Q from P this time because P is the same as Q in equilibrium in this equation)
Add them up: x + 2x + 2 - 2x = x + 2 so B is the correct answer

 

[izzahzainab]

How many isomeric esters have the molecular formula C4H8O2?
A 2 B 3 C 4 D 5
HELP!!!

Methyl propanoate (CH3-CH2-COO-CH3)

Ethyl ethanoate (CH3-COO-CH2-CH3)

Propyl methanoate (HCOO-CH2-CH2-CH3)

2-methyl-ethyl methanoate (HCOO-CH-(CH3)2)
so there are 4 isomers.

 

[magnesium]

3) When an isomer Y of molecular formula C4H9Br undergoes hydrolysis in aq. alkali to form an alcohol C4H9OH, the rate of reaction is found to be unaffected by changes in concentration of the OH- ions present. Which is the most likely molecular structure of Y?

A CH3CH2CH2CH2Br
B CH3CH2CHBrCH3
C (CH3)2CHCH2Br
D (CH3)3CBr
the ans is D
bcoz CH3 is electron supplying group ~ the CH3 - C bond becomes stronger

 

[magnesium]

Kp is only effected by temperature