Chemistry MCQ thread...

[Zishi]

B.

 

[hassam]

yea tru..

 

[abdullah181994]

please answer this with working

 

[xHazeMx]

its B right ? just to make sure. in case if the enthalpy change of formation is to be calculated, we subtract reactants from products right?

 

[kakarocks]

Is it A - 0.03 mol/dm3 ?

If yes than - here is how to do it

no of mole of nitrogen in 100 g of fertilizer = 15/14 =mass/mr = 1.07

no of moles in 14g of fertilizer = 1.07 X 14 / 100 =0.1498

now these are no of moles in 5 dm3 so in 1 dm3 = .1498/5 =.02996 ~ 0.03 !

 

[Saturation]

How do you do number 7!? (please show full working!)

http://www.xtremepapers.me/CIE/Internat ... 5_qp_1.pdf

Anyone? :good:

Is it C? -81

yes, but how do you calculate it!?

 

[xHazeMx]

answer showing ur working

 

[kakarocks]

14/2 = 7 because its two moles being formed and -88 +7 = -81 answer!

 

[kakarocks]

answer showing ur working

Already did look above!

 

[Zishi]

yes, but how do you calculate it!?

Enthalpy change of formation is from products. According to equation one mole of ICl is being used to form one mole of ICl3, so you'd have to divide first enthalpy change by 2, then add it into second enthalpy change to get enthalpy change of formations of ICl3 - as enthalpy change of formation of anything is its one mole from any number of moles of elements.

 

[MHHaider707]

answer showing ur working

Its A.....

100 g of fertilizer contain 15 g of nitrogen
14 g will contain 2.1 g of nitrogen

Now moles of nitrogen = 2.1/14 =0.15 moles

concentration = 0.15/5 =0.03 mol dm^-3

 

[abdullah181994]

please answer with explanation correct answer is C

 

[xHazeMx]

please answer with explanation correct answer is C

there is a formula for this kind of questions which is ( 2^n ) where n indicates the number of double bonds. there are 3 double bonds so 2^3 = 8

 

[kakarocks]

Ummm 2^3 -1 = 7 not 8

 

[xHazeMx]

Ummm 2^3 -1 = 7 not 8

sorry its 2^n only :roll:

 

[abdullah181994]

Q Which compound has a boiling point which is influenced by hydrogen bonding ?

A. CH3CHO
B. CH3OCH3
C. HC02H
D HC02CH3

please explan it to me with answer !!

C is correct because it is carboxylic acid and Carboxylic acid have hydrogen bonding between them they form dimmer .

 

[histephenson007]

Q Which compound has a boiling point which is influenced by hydrogen bonding ?

A. CH3CHO
B. CH3OCH3
C. HC02H
D HC02CH3

please explan it to me with answer !!

C is correct because it is carboxylic acid and Carboxylic acid have hydrogen bonding between them they form dimmer .

But D is a carboxylic acid too! wouldn't the answer be A??

 

[xHazeMx]

why is it 1 only ? why 2 is wrong?

 

[abdullah181994]

Q Which compound has a boiling point which is influenced by hydrogen bonding ?

A. CH3CHO
B. CH3OCH3
C. HC02H
D HC02CH3

please explan it to me with answer !!

C is correct because it is carboxylic acid and Carboxylic acid have hydrogen bonding between them they form dimmer .

But D is a carboxylic acid too! wouldn't the answer be A??

D is an ester while A is an aldehyde and in aldehde hydrogen is not attached to oxygen,for hydrogen bonding hydrogen should be attached to very electronegative atoms
i.e flourine,oxygen or nitrogen u could memorize this by word FON.

 

[abdullah181994]

why is it 1 only ? why 2 is wrong?

As the temprature increases pressure also increases it does not remian constant.