Biology; Chemistry; Physics: Post your doubts here!

[malay]

oh ok ill try dat thnkss

no prob

 

[Rimsa]

Q/9
http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Chemistry (5070)/5070_w09_qp_1.pdf
how come the answer is D?

if we have two Hydrogen-1; 18
if we have two Hydrogen-2; its 20
if we have one hydrogen-1 and one hydrogen-2; its 19

 

[malay]

if we have two Hydrogen-1; 18
if we have two Hydrogen-2; its 20
if we have one hydrogen-1 and one hydrogen-2; its 19

thanx a bunch

 

[Dukeofwin]

hahaa.... woww!! thanks God i didn't do anything to get that much insult. *phew*
Dukeofwin i wasn't getting scared .... i was just trying to show some respect in these not-so-deserving circumstances .... besides no one deserves that kind of battering to begin with we all have probably torn his hide off already.

Roses are Red
Violets are Blue
People are so rude
For which i don't have a Clue!

 

[A star]

in the transformer question what was the power loss?

 

[Dukeofwin]

in the transformer question what was the power loss?

I used P=I^2xR
The answer I got was 12.1 Watts!
And you?

 

[A star]

i added resistance of the bulb in it as it said both leads how can you lose power in both leads without lamp.my physics sir confirmed it.. it is the only question where i will lose marks. about 1-4 marks in will lose both papers. but i will scrape a A* i know it.

 

[A star]

iam not worried as using i2 R will give yu 1 marks so max loss is two

 

[Dukeofwin]

i added resistance of the bulb in it as it said both leads how can you lose power in both leads without lamp.my physics sir confirmed it.. it is the only question where i will lose marks. about 1-4 marks in will lose both papers. but i will scrape a A* i know it.

You shouldn't have mentioned it!
Your name tells the Story!

 

[ashiqbal]

heyy need help in the question 28 from 5070_s10_qp_12. please explain it too.
sorry for not posting the link bcuz i cant open the paper ryt now .... the connection is too darn slow!! -__-

the question is like this: the same mass is used every time, right? let mass be x
then moles of zinc = x/65
moles of magnesium = x/24
the equation for both reaction is same, so one mole of metal produces 1 mole of hydrogen.
therefore, moles of H2 with zinc = x/65, whereas moles of H2 with Mg = x/24!
x/24 is greater, so greater volume with magnesium!

 

[ashiqbal]

You answered your own question
Rate of reaction is the main point here.For the same time , magnesium will react quickly and yield more than zinc that reacts slowly. It's like the fast athlete will be able to complete 2 laps , while the slower athlete will only be able to complete 1 lap for the same amount of time . Simple concept hai Sister, don't confuse yourself!

As for the matter of mixture , well that is obvious! It cannot give maximum yield as part of both metals will be shielded by the other metal . And it won't give minimum as both metals are collectively reacting . So it would give yield of somewhere in between.

wrong explanation! see my explanation given above!

 

[ashiqbal]

Question!
From which ammonium salt can the greatest mass of ammonia b obtained?
A) 0.5 mole (NH3)2PO4
B) 0.5 mole (NH4)2SO4
C) 1 mole NH4Cl
D) 1 mole NH4NO3
PLZ do explain

guess its D, which year past paper? tell me the answer then ill give you the explanation!

 

[A star]

guess its D, which year past paper? tell me the answer then ill give you the explanation!

you are absolutely correct

 

[snowbrood]

 

[snowbrood]

what are physical properties depended upon i thought mass but i think i am wrong correct me guys

 

[Dukeofwin]

View attachment 11038View attachment 11039

I guess,
27=D
12=c
?

 

[Dukeofwin]

what are physical properties depended upon i thought mass but i think i am wrong correct me guys

They depend upon element's Electronic Configuration!

 

[A star]

View attachment 11038View attachment 11039

27a and 12c. duke displacement reaction requires no heat you know.

 

[MustafaMotani]

Reactivity series !
Please (K) send (Na) cats (Ca) monkeys (Mg) and (Al) Zebras (Zn) In (Fe) large (Pb) huge (H) cage (Cu) . Make (Hg) sure(Ag) packed/padlocked (Pt)

Hope it helps, it did help me

 

[snowbrood]

27a and 12c. duke displacement reaction requires no heat you know.

WHY DOES THE QUESTION SAYS THAT THE REACTION DOES NOT TAKE PLACE AT ROOM TEMP