Chemistry MCQ thread...

[Hateexams93]

One carbon has 3, and another one has 4. and of course, all H atoms have 1.

check 1 again carbon is reduced and oxidised check the oxidation numbers of C2 and C3 in the products

I guess I concentrated on one carbon atom only. You were correct.

i still didn't get it , why ?? isn't it the same ?((

 

[Zishi]

check 1 again carbon is reduced and oxidised check the oxidation numbers of C2 and C3 in the products

I guess I concentrated on one carbon atom only. You were correct.

no problem u r still the master

LOL! No, no, I'm not. Thanks anyway.

And no, 'negligible heat capacity of calorimeter' hasn't got anything to do with it. We need specific heat capacity of sulfuric acid.

 

[xHazeMx]

i still didn't get it , why ?? isn't it the same ?((

nope, check C2 and C3 they have different oxidation numbers .. remember that the total oxidation number should be zero in any compound

 

[xHazeMx]

LOL! No, no, I'm not. Thanks anyway.

And no, 'negligible heat capacity of calorimeter' hasn't got anything to do with it. We need specific heat capacity of sulfuric acid.

you welcome, i think the question is wrong then :/

 

[abdullah181994]

Hi pros here.. please help me

3 The foul smell that skunks spray is due to a number of thiols, one of which is methanethiol,
CH3SH, which burns as follows.
CH3SH + 3O2 → CO2 + SO2 + 2H2O
A sample of 10 cm3 of methanethiol was exploded with 60 cm3 of oxygen.
What would be the final volume of the resultant mixture of gases when cooled to room
temperature?
A 20 cm3 B 30 cm3 C 50 cm3 D 70 cm3

19 Ammonium sulphate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing
sulphuric acid, nitric acid and water.
How many moles of oxygen are needed to oxidise completely one mole of ammonium sulphate?
A 1 B 2 C 3 D 4

and please help me with oct nov 04 no 10 11 12 and 21.. i cant paste it here because there are pictures and tables..

first construct a chemical equation from there u could get your answer.


3:C because 30cm3 of O2 does not reacted +10cm3 of CO2+10cm3 of SO2
19:A not sure

3 is C, how can you find 30 cm3 of 02?
19 is D, can you explain why it is D??
thank you so much btw

can others help me with oct nov 04 no 10,11,12 and 21??

 

[Hateexams93]

CAN SOME1 plzz expain the answer

 

[abdullah181994]

@kirashinagami 1 mole of CH3SH REACTED WITH 3 MOLES OF O2
SO 10CM3 OF CH3SH WOULD REACT WITH 3 X10CM3 OF O2=30CM3
TOTAL VOLUME -VOLUMEM OF O2 USED=60-30=30CM3

 

[xHazeMx]

CAN SOME1 plzz expain the answer

B .. it will form both ( pent 1 ene and pent 2 ene ) other compounds will form just 1 type of alkene

 

[kshumaila52]

CAN SOME1 plzz expain the answer

AnS B
3 different alkenes (including 2 Cis trans)

 

[KrazyMano]

Hi pros here.. please help me

3 The foul smell that skunks spray is due to a number of thiols, one of which is methanethiol,
CH3SH, which burns as follows.
CH3SH + 3O2 → CO2 + SO2 + 2H2O
A sample of 10 cm3 of methanethiol was exploded with 60 cm3 of oxygen.
What would be the final volume of the resultant mixture of gases when cooled to room
temperature?
A 20 cm3 B 30 cm3 C 50 cm3 D 70 cm3

19 Ammonium sulphate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing
sulphuric acid, nitric acid and water.
How many moles of oxygen are needed to oxidise completely one mole of ammonium sulphate?
A 1 B 2 C 3 D 4

and please help me with oct nov 04 no 10 11 12 and 21.. i cant paste it here because there are pictures and tables..

I have the same query regarding 19. Please can someone tell me how to solve it???? Pleease

 

[Xthegreat]

question 19

just write out the equation and balance. quite easy

(NH4)2SO4 + 4O2 -> H2SO4 + 2HNO3 + 2H2O

 

[hassam]

ZISHI...1 IS ALSO CORRECT AND ITS a... JUst stick with the use of oxidation numbers

No, I'll stick with C 'til I get it confirmed. Is A given in the mark scheme OR a book?

its A in markscheme !!!,,,,,,,u u dont think 1ST option to be ryt

 

[xHazeMx]

ZISHI...1 IS ALSO CORRECT AND ITS a... JUst stick with the use of oxidation numbers

No, I'll stick with C 'til I get it confirmed. Is A given in the mark scheme OR a book?

its A in markscheme !!!,,,,,,,u u dont think 1ST option to be ryt

he has already figured it out later on

 

[KrazyMano]

question 19

just write out the equation and balance. quite easy

(NH4)2SO4 + 4O2 -> H2SO4 + 2HNO3 + 2H2O

Mm hehe didn occur to me I think chemistry is goin to my brains lol!! Thanku so much

 

[kirashinagami]

question 19

just write out the equation and balance. quite easy

(NH4)2SO4 + 4O2 -> H2SO4 + 2HNO3 + 2H2O

heyy do you have any tips and tricks on balancing equations, i really suck at that

 

[hassam]

Astatine (At) is a Group VII element. Its properties are not easily studied due to its
short half life and low natural abundance. However, its properties can be deduced
from the trends of other Group VII elements. Which of the following statements
about astatine are likely to be correct?
1 HAt is a stronger acid compared to HCl.
2 At2 disproportionates in cold dilute sodium hydroxide to yield AtO3
- and At - as
major products.
3 Potassium astatide forms a precipitate with silver nitrate quickly and can dissolve
in dilute aqueous ammonia solution.

 

[Anonymousx3]

Astatine (At) is a Group VII element. Its properties are not easily studied due to its
short half life and low natural abundance. However, its properties can be deduced
from the trends of other Group VII elements. Which of the following statements
about astatine are likely to be correct?
1 HAt is a stronger acid compared to HCl.
2 At2 disproportionates in cold dilute sodium hydroxide to yield AtO3
- and At - as
major products.
3 Potassium astatide forms a precipitate with silver nitrate quickly and can dissolve
in dilute aqueous ammonia solution.

D? Or maybe B?
I'm not sure.

 

[xHazeMx]

Astatine (At) is a Group VII element. Its properties are not easily studied due to its
short half life and low natural abundance. However, its properties can be deduced
from the trends of other Group VII elements. Which of the following statements
about astatine are likely to be correct?
1 HAt is a stronger acid compared to HCl.
2 At2 disproportionates in cold dilute sodium hydroxide to yield AtO3
- and At - as
major products.
3 Potassium astatide forms a precipitate with silver nitrate quickly and can dissolve
in dilute aqueous ammonia solution.

D right ?

 

[Zishi]

Astatine (At) is a Group VII element. Its properties are not easily studied due to its
short half life and low natural abundance. However, its properties can be deduced
from the trends of other Group VII elements. Which of the following statements
about astatine are likely to be correct?
1 HAt is a stronger acid compared to HCl.
2 At2 disproportionates in cold dilute sodium hydroxide to yield AtO3
- and At - as
major products.
3 Potassium astatide forms a precipitate with silver nitrate quickly and can dissolve
in dilute aqueous ammonia solution.

D

 

[xHazeMx]

Astatine (At) is a Group VII element. Its properties are not easily studied due to its
short half life and low natural abundance. However, its properties can be deduced
from the trends of other Group VII elements. Which of the following statements
about astatine are likely to be correct?
1 HAt is a stronger acid compared to HCl.
2 At2 disproportionates in cold dilute sodium hydroxide to yield AtO3
- and At - as
major products.
3 Potassium astatide forms a precipitate with silver nitrate quickly and can dissolve
in dilute aqueous ammonia solution.

A

no way ! :%)