Mass of solution was 250 cm^3. Raise by 25 degrees C. Enthalphy change for CaO was -196.8.

0.25 x 4.18 x 25 = 26.125 kJ needed

moles of CaO needed is 26.125/196.8=0.1327 moles

Mass of CaO is 0.1327 x (40.1+16)= 7.45g (3s.f)

Reply 986

Nur97

For the enthalpy question wasn't it 50.0 x 4.18 x 19.5? (Difference between initial and final temperature?)

Reply 987

SuperVegito

What grade would one get if they have 60%A and 40%U?

Reply 988

lfcrules

What did people put for the multiple chocie question about the yiwl of hydrogen ibput the one about the layer of oil

Reply 989

Medically

Original post by lfcrules

What did people put for the multiple chocie question about the yiwl of hydrogen ibput the one about the layer of oil

Same!!!

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Reply 990

lfcrules

Original post by Nur97

For the enthalpy question wasn't it 50.0 x 4.18 x 19.5? (Difference between initial and final temperature?)

The initial temp was 19.5 final was 35 giving a change of 15.5

Reply 991

dexirion

For the mass of calcium oxide question I done 250x4.18x25=26125J
Then 194( or whatever the value was)
194kJ=26.125kJ/moles
So to get moles you do
26.125kJ/194kJ = 0.135moles
And finally
0.135x56.1(Mr of CaO)=7.55g

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Reply 992

Medically

Original post by lfcrules

What did people put for the multiple chocie question about the yiwl of hydrogen ibput the one about the layer of oil

Because there is no oil in the following reaction they have given to you

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Reply 993

ashnutking

Original post by lfcrules

What did people put for the multiple chocie question about the yiwl of hydrogen ibput the one about the layer of oil

yh same here - was a bit of a guess tho

Reply 994

C0balt

Original post by lfcrules

What did people put for the multiple chocie question about the yiwl of hydrogen ibput the one about the layer of oil

I said Hydrogen is soluble in water statement
Hydrogen can only form dispersion intermolecular force so cannot dissolve in water as much? All seemed legit though

It said to choose wrong one righ?

Reply 995

AA10743

Original post by Medically

I wrote 124.5 instead of 125, would I lose marks?

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yes, you'll lose 8. Question specifically asked for number of legs

Reply 996

nishab_

Original post by Nur97

For the enthalpy question wasn't it 50.0 x 4.18 x 19.5? (Difference between initial and final temperature?)

Yeah that's what I got :smile:

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Reply 997

Whizbox

For the steroids I said ensure that the drug did not have the same mass of an allowed substance that may be in urine and take large samples just in case the drug is not very abundant

Reply 998

Medically

Original post by C0balt

I said Hydrogen is soluble in water statement
Hydrogen can only form dispersion intermolecular force so cannot dissolve in water as much? All seemed legit though

It said to choose wrong one righ?