Chemistry MCQ thread...

[MHHaider707]

Magnessium because they are same period, maybe!

its beryillium. the listed choices are all from group 2. so the one on the top has the highest charge density as it has the least ionic/atomic radii. so the answer is Beryillium.

I didn't get it!!!

it does not justify that Be have same electronegativity as of Aluminium!!

 

[xHazeMx]

http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_s08_qp_1.pdf Q 23, 26, 27, 30 AND 39

PLEASE SOLVE THEM !!! THNX I DONT HAV SCREEN SHOT OPTION

please solve them !! ill be thnkful to u guys !!

Q 23, its D because compounds having carbon atoms from 1 - 4 are gases which can be collected in the inverted tube because they r gases
Q 26, its C because 2 atoms of oxygen are added and 4 H atoms are removed indicating that after oxidation there are 2 carboxilic groups ( COOH ) and this would be the result from primary alcohols only so the OH should be on the first and fourth carbon
Q 27, its D because it is the result of dehydrating tertiary alcohol which is unreactive towards mild oxidising agents.
Q 30, its C because the X has been oxidised to an acid ( having 6 C atoms , hexanoic acid ) added to ethanol alcohol to produce an ester. the group behind the COO group is the acid formed by compound X
Q39, its B ( 1 and 2 ) because there are a secondary alcohol group which doesn't form aldehyde on oxidation but it reacts with sulphuric acid forming an ester, when bromine is added to cholesterol, it forms 2 new chiral carbons. u can figure them out easily
i hope this helps u

 

[sakibfaiyaz]

Magnessium because they are same period, maybe!

its beryillium. the listed choices are all from group 2. so the one on the top has the highest charge density as it has the least ionic/atomic radii. so the answer is Beryillium.

I didn't get it!!!

it does not justify that Be have same electronegativity as of Aluminium!!

Its a fact that elements which have a diagonal relationship in the periodic table will have similar chemical properties.
Be and Al form a diagonal!

 

[xHazeMx]

@sakibfaiyaz .. Thats right, now it is justified. i dunno i completely understood it in a different way :roll:

 

[smartangel]

please explain June 03 question 2.

The answer is B, 5 moles of Hydrogen.

how do you get 5? please explain.

 

[xHazeMx]

please explain June 03 question 2.

The answer is B, 5 moles of Hydrogen.

how do you get 5? please explain.

2 molecules are formed by using 4 moles of hydrogen ( 2 hydrogen moles in each molecule, as 2 double bonds are hydrogenated in each molecule ) and 1 molecule is formed by using 1 mole of hydrogen to hydrogenate 1 double bond. So, the total is 5 moles of hydrogen

 

[maybeitwasnoone]

The answer is B, 5 moles of Hydrogen.

how do you get 5? please explain.

2 molecules are formed by using 4 moles of hydrogen ( 2 hydrogen moles in each molecule, as 2 double bonds are hydrogenated in each molecule ) and 1 molecule is formed by using 1 mole of hydrogen to hydrogenate 1 double bond. So, the total is 5 moles of hydrogen

An easier way is to just count the number of Hydrogen in both compounds and subtract.

 

[Saturation]

For the electonegativitey qs.
can you please explain the "diagonal fact" as in like, how we form the diagonal!?

 

[sakibfaiyaz]

For the electonegativitey qs.
can you please explain the "diagonal fact" as in like, how we form the diagonal!?

http://en.wikipedia.org/wiki/Diagonal_relationship

 

[xHazeMx]

Concentrated sulphuric acid is added to separate solid samples of sodium chloride, sodium
bromide or sodium iodide.
With which sample(s) does sulphuric acid act as an oxidising agent?
A sodium chloride only
B sodium chloride and sodium bromide
C sodium bromide and sodium iodide
D sodium iodide only

what could be the answer ?

 

[sakibfaiyaz]

C
its in the book..its a fact!

 

[mizmoody]

june 2002 Q21 and Q39 plxxx???

 

[Mssamgirl15]

OCTOBER/NOVEMBER 2008 QUESTION 4:


Use of the Data Booklet is relevant to this question.
Hard water contains calcium ions and hydrogencarbonate ions arising from dissolved calcium
hydrogencarbonate, Ca(HCO3)2.
How many electrons are present in the hydrogencarbonate anion?
A 30
B 31
C 32
D 33

This question is probably extremely simple, I just can't figure it out. Help please. :/

 

[mizmoody]

helppp... my moles concepts r rly weak! =((

 

[mizmoody]

the answer is D .. y?

 

[Hateexams93]

Can some1 plz explain this

 

[Saturation]

READ THE NEXT POSTS PLEASE! (This was a double post, and I couldn't delete it :no: )

 

[Saturation]

Can some1 plz explain this

OCTOBER/NOVEMBER 2008 QUESTION 4:


Use of the Data Booklet is relevant to this question.
Hard water contains calcium ions and hydrogencarbonate ions arising from dissolved calcium
hydrogencarbonate, Ca(HCO3)2.
How many electrons are present in the hydrogencarbonate anion?
A 30
B 31
C 32
D 33

This question is probably extremely simple, I just can't figure it out. Help please. :/

Hydrogencarbonate anion is formed when H2CO3 (carbonic acid) ,looses a Hydrogen ion ( proton), which means it has the same number of electrons as H2CO3.
Total electrons: 2+6+(3 x8) = 32, so it must be C.

helppp... my moles concepts r rly weak! =((

the formula is: number of MOLES = volume/ 24 (this is because at rtp. 1 mole of any gas occupies 24 dm3)
so the number of MOLES = 0.5dm3 / 24 = 0.0208..... (which is 1/48 moles)
1 mol contains 6.02 X 10^23 particles, so 0.0208 mol must contain 6.02 X 10^23 X 0.0208, which is 1.25 x 10^22

In this case the particles are molecules, so the answer must be A.

the answer is D .. y?

I always mess up these type of questions! Apparently, I find out how many possible combinations can exist, but every time, the actual amount is higher, so someone ples explain! :%)

 

[Saturation]

Can some1 plz explain this

For the reactions of gases at rtp, you can use the reacting volumes of the gasses as the molar ratio of the equation.

Form combustion equations for the 1st and last alkanes.

CH4+2O2 = CO2 + 2H20

So it will become:

10 cm3 of CH4 react with 20 cm3 of O2 to give 10cm3 of CO2 ( This doesnt apply to H2O, since it's liquid)

So if 10cm3 of methane reacted with 20cm3 of oxygen, the left over O2 is 50cm3, and since they ask the TOTAL volume of gasses, we add the 10cm3 of CO2 produced, giving us 60cm3.

Do the same for the last alkane (C4H10) , and then plot the 2 points and find the trend!

 

[Saturation]

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

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