Biology; Chemistry; Physics: Post your doubts here!

[Amnaa]

A 25 cm3 sample of dilute sulphuric acid contains 0.025 moles of the acid.
What is the hydrogen ion concentration in the solution?
A
0.25 mol / dm3
B
0.50 mol / dm3
C
1.00 mol / dm3
D
2.00 mol / dm3

 

[Saad Mughal]

A 25 cm3 sample of dilute sulphuric acid contains 0.025 moles of the acid.
What is the hydrogen ion concentration in the solution?
A
0.25 mol / dm3
B
0.50 mol / dm3
C
1.00 mol / dm3
D
2.00 mol / dm3

Concentration of Acid = Concentration of H+,
Therefore,
Concentration = 0.025/(25/1000) = 1 mol./dm^3.
Answer C.

 

[Amnaa]

h

Concentration of Acid = Concentration of H+,
Therefore,
Concentration = 0.025/(25/1000) = 1 mol./dm^3.
Answer C.

The answer is D.. according to the marking scheme

 

[Buland Iqbal]

h

The answer is D.. according to the marking scheme

Yes, it is indeed D. You see that one mole of Sulphuric acid gives two hydrogen ions, i.e H2SO4 gives 2H+. This concept will be applied. That is why, the concentration of sulphuric acid x 2= Concentration of H+ ions.

 

[asma tareen]

Concentration of Acid = Concentration of H+,
Therefore,
Concentration = 0.025/(25/1000) = 1 mol./dm^3.
Answer C.

i guess u missed out a step we have 2 atoms of hydrogen so we should multiply the answer by 2

 

[Buland Iqbal]

i guess u missed out a step we have 2 atoms of hydrogen so we should multiply the answer by 2

Let me use an ionic equation for clarification. H2S04--->2H+ + S04 2-. In this way, the answer can be worked out.

 

[Saad Mughal]

i guess u missed out a step we have 2 atoms of hydrogen so we should multiply the answer by 2

h

The answer is D.. according to the marking scheme

Well, yeah, sorry. Asma's right. H2SO4 contains 2 hydrogen ions so it had to be multiplied by 2.

 

[asma tareen]

Well, yeah, sorry. Asma's right. H2SO4 contains 2 hydrogen ions so it had to be multiplied by 2.

dekh lo dadi itni naa layk nai hai

 

[Saad Mughal]

dekh lo dadi itni naa layk nai hai

...
No comments.

 

[asma tareen]

...
No comments.

 

[papajohn]

I m worrying about this same question come in our Atp..

 

[Amnaa]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s03_qp_1.pdf
QUESTION NO.31

 

[Amnaa]

i

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s03_qp_1.pdf
QUESTION NO.31

is it the correct way to solve this question..
as in air about 20% is oxugen soo.. 20/100(80)=16
80-16=64??

 

[asma tareen]

well air contains about 20 % oxygen so 20/100*8o=16
16 cm3 would react 80 - 16 64 cm3
C is the answer i think

 

[usama321]

yayyyy at last people are not discussing bio anymore

 

[AhsanAfzal]

Consider the formula P=I^2R, If resistance is kept constant and the power is decreased, the current would increase.
Similarly, as asked in the question, if the power is decreased, the current would increase hence there is a risk of over heating.
For part (ii), if the power is increases, the current would decrease, this means that very little current would pass through because of the high resistance.

P=I^2R , if power decreases shouldnt current also decrease? P should be directly proportion to square of I if R is constant

 

[Saad Mughal]

yayyyy at last people are not discussing bio anymore

I pounced on the first question that I saw non-biology related. Its a relief from all that epidermal and complicated internal structure discussions. ._.

 

[Saad Mughal]

P=I^2R , if power decreases shouldnt current also decrease? P should be directly proportion to square of I if R is constant

It is proportional to the square of I, so it will decrease, you can try putting values of P and check the results.

 

[AhsanAfzal]

It is proportional to the square of I, so it will decrease, you can try putting values of P and check the results.

thnks

 

[usama321]

It is proportional to the square of I, so it will decrease, you can try putting values of P and check the results.

should not it increase too?