Chemistry MCQ thread...

[workinghard]

@ hassam its SO2!

 

[Dobby1287]

34 Which statements concerning the third period elements (sodium to argon) and their compounds
are correct?
1 The elements become more electronegative from sodium to chlorine.
2 Aluminium oxide is the only oxide which is insoluble in water.
3 The maximum oxidation state is shown by silicon.

 

[workinghard]

D!

 

[workinghard]

i meant 1 only!!!
highest oxidation is shown by Cl n SiO2 is insoluble 2

 

[sadman]

Guys, i have a number of questions and cud you please help me solve it??
All of them are from november 2010 qp 12
q12
answer was D buti gave B..isnt MgO much more stable than the oxide od strontium?
q18
how can bromine vapour be purple?????
q 20
i tires drawing but only cud draw till 4
these were:
Cl3C- CH2 - CH3 CClH2 - CClH - CClH2 CH3 - CCl2 - CClH2 CCl2H - CClH - CH3
q 34
both the reaction gives out same amount of hydrogen....why will sulfuric acid give more?? i know that sulfuric acid is the stronger one, but the question says the reaction was COMPLETE after 20 min! can anyone justify the third statement?

 

[sadman]

there is another one also
q38 nov 2010 12
if there are 4 carbon how can 2 and 3 be correct?? what do have to consider here number of oxygen atom?? is CIE assuming that we shud be able to apply our knowledge that any of the peroducts cud be synthesized ( in 2 and 3 ) e.g with hydrogen cyanide or smthin?? thats one of the alchooles axidized to ketones or aldehydes and then by hydrogen cyanide?

 

[sadman]

there is another one also
q38 nov 2010 12
if there are 4 carbon how can 2 and 3 be correct?? what do have to consider here number of oxygen atom?? is CIE assuming that we shud be able to apply our knowledge that any of the peroducts cud be synthesized ( in 2 and 3 ) e.g with hydrogen cyanide or smthin?? that is one of the alcholos oxidized to ketones or aldehydes and then by hydrogen cyanide?

 

[abdullah181994]

34 Which statements concerning the third period elements (sodium to argon) and their compounds
are correct?
1 The elements become more electronegative from sodium to chlorine.
2 Aluminium oxide is the only oxide which is insoluble in water.
3 The maximum oxidation state is shown by silicon.

D because SiO2 also insoluble

 

[sadman]

CAN AnY ONE HELP ME????

 

[kirashinagami]

27- B
first one can not be dehydrated!!


28- B
Duetrium will substitute H atom of (OH) group so three OH groups r present....


35- A
All reactions occur in soil when lime is added!!!

thanks MHHaider for answering my question..

27. what is the reason it cannot be dehydrated? primary alcohol cannot be dehyraded?why?
28. why it should replace H? what reaction is this?which chapter of AS?
29. is this logic or must be memorized?? hehehe .

 

[workinghard]

it would b better if u could post da questions here
if dey r without any fig copy n paste dem otherwixe use da print/screen button on keyboard as i assume zishi suggested n paste in paint n den attach da file ...

 

[xHazeMx]

34 Which statements concerning the third period elements (sodium to argon) and their compounds
are correct?
1 The elements become more electronegative from sodium to chlorine.
2 Aluminium oxide is the only oxide which is insoluble in water.
3 The maximum oxidation state is shown by silicon.

its D, silicon dioxide is insoluble in water too and the maximum oxidation is shown by chlorine

 

[xHazeMx]

it would b better if u could post da questions here
if dey r without any fig copy n paste dem otherwixe use da print/screen button on keyboard as i assume zishi suggested n paste in paint n den attach da file ...

here is the way to post ur questions. take a screenshot of the question u want open the program (paint). press (ctrl+v). crop the margins of the question showing only the question. save the file with the extension (.png) , then attach the file in ur post here

 

[smartangel]

In an experiment, b mol of hydrogen iodide were put into a sealed vessel under pressure p. At
equilibrium, x mol of the hydrogen iodide had dissociated, the reaction being represented by the
following equation.
2HI(g) H2(g) + I2(g)
Which expression for Kp is correct?

A___x_2__
4(b – x)2

B__x_2_p_2__
4b(b – x)


C__x_2_p_2_
(b – x)2

D___x_2__
(b – x)2

 

[gary221]

errr.... just 1 thing
r u guys talking about the igcse papers ???????????????????
coz if yes , i never in my life saw such ques. :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%)

 

[MHHaider707]

In an experiment, b mol of hydrogen iodide were put into a sealed vessel under pressure p. At
equilibrium, x mol of the hydrogen iodide had dissociated, the reaction being represented by the
following equation.
2HI(g) H2(g) + I2(g)
Which expression for Kp is correct?

A___x_2__
4(b – x)2

B__x_2_p_2__
4b(b – x)


C__x_2_p_2_
(b – x)2

D___x_2__
(b – x)2

Its A.....!!

when x moles r dissociated then the moles of HI at equilibrium = b - x!!

2 moles of HI give 1 mole of H2 and I2 and x moles give (x/2) moles!!

make an expression for Kp
(x/2)^2 x (x/2)^2
kp = ----------------------
(b - x)^2


it will give the xpression for Kp n ans. will be A!!

 

[xHazeMx]

In an experiment, b mol of hydrogen iodide were put into a sealed vessel under pressure p. At
equilibrium, x mol of the hydrogen iodide had dissociated, the reaction being represented by the
following equation.
2HI(g) H2(g) + I2(g)
Which expression for Kp is correct?

A___x_2__
4(b – x)2

B__x_2_p_2__
4b(b – x)


C__x_2_p_2_
(b – x)2

D___x_2__
(b – x)2

its A, x mole of HI has dissociated so mole of H2 is x/2 and I is x/2. HI had initial moles b, after dissociation its b - x ( since x moles has dissociated ) .. gathering all these information in Kc we would get A as the answer ( Kc= x^2 / 4(b - x)^2 )

 

[xHazeMx]

errr.... just 1 thing
r u guys talking about the igcse papers ???????????????????
coz if yes , i never in my life saw such ques. :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%) :%)

not all of the questions are from the igcse papers. some are from cambridge chemistry books

 

[gary221]

oops sorry figurd it out>>>>>>>>>

 

[xHazeMx]

someone show the calculations for this question