Physics, Chemistry and Biology: Post your doubts here!

[Lanocaster]

I have a doubt in physics -
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_qp_32.pdf
Question 2
Marking scheme:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_ms_32.pdf

That's an easy question:
a) The resultant will be towards the left because centripetal force is acting on the airliner
b) You have to draw a parallelogram, and find the diagonal length. That will be the resultant
c) The velocity is constantly changing because the direction is changing

 

[ashutosh rungta]

can somebody please tell me about logic gates in physics
i have my exam on the 14th of november physics paper 32

 

[ashutosh rungta]

as soon as possible.. plz, plz,plz

 

[Faheen]

Can anybody plz tell me how to solve Q8bi) from this link........plz
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Science - Combined (0653)/0653_s11_qp_31.pdf

 

[themessers1000]

guys i have a physics exam in 3 hours and i need help, the electrons is said to have the lowest mass, when a question comes up saying does electrons have mass or not, what do i say?

 

[themessers1000]

guys i have a physics exam in 3 hours and i need help, the electrons is said to have the lowest mass, when a question comes up saying does electrons have mass or not, what do i say?

 

[TheOnlyOne]

guys i have a physics exam in 3 hours and i need help, the electrons is said to have the lowest mass, when a question comes up saying does electrons have mass or not, what do i say?

Dont say anything WRITE !!

 

[SREYAh]

can you help me please...
1: what mass of ammonia would be evolved by heating together 100g of ammoniun chloride, NH(4)Cl and 70g of calcium hydroxide Ca(OH)(2)?
2: 4.6g of sodium metal are added slowly to 10g of water in a small dish. what is the total mass of the solution left when the reaction is completed?
can you solve this for me please... i will be very grateful to you..
and show me your workings please...

 

[Tiffygirly]

Has anyone done any of the varient of Biology Paper 1? How was it??

 

[khochloe]

physics
9702/04/O/N/08
question 1
a (iii) and b(i)
help ... thanks ^_^

 

[themessers1000]

Has anyone done any of the varient of Biology Paper 1? How was it??

ive done the variant 12, and it was good but i wanted more marks i felt, and now for 6 hours ive been thinking what will happen to me if i fail biology core, i really need help to get this stress out of me but im literally shaking

 

[Tiffygirly]

You've done your best dude. Don't be scared,if u prepared well. Good to know that ur objectives went on well

 

[themessers1000]

You've done your best dude. Don't be scared,if u prepared well. Good to know that ur objectives went on well

thank you :') when i opened the grade threshold for biology, there are two tables, the first table has the grades and their marks and last year a D was only 50% for core, is it true that in november exams the curve is always lower?

 

[Tiffygirly]

I have no idea about that,sorry.

 

[themessers1000]

I have no idea about that,sorry.

how did you find paper 1?

 

[Tiffygirly]

It was ok

 

[Tiffygirly]

It was ok

 

[snipex]

can you help me please...
1: what mass of ammonia would be evolved by heating together 100g of ammoniun chloride, NH(4)Cl and 70g of calcium hydroxide Ca(OH)(2)?
2: 4.6g of sodium metal are added slowly to 10g of water in a small dish. what is the total mass of the solution left when the reaction is completed?
can you solve this for me please... i will be very grateful to you..
and show me your workings please...

Well for question (1) you will start by writing the equation and balancing it(2NH4cl + ca(oh)2 = cacl2 +2h2o+2NH3)then you find number of moles of NH4cl ir ca(oh)2 . I will use ca(oh)2. It will be 70/(40.1+16+16+2) to get 0.94 then ratio of calcium hydroxide to ammonia is 1:2 so 0.94x2 to get mole of ammonia that is 1.88. After that get molecular mass of ammonia and multiply it by number of moles you get to find the mass.
For(2) you start by writing balnced equation, get mole of sodium and compare it to hydrogen then get mass of hydrogen evolved and subtract it from total mass. Easy right?

 

[Muskan Achhpilia]

Chemistry doubt-

The answer is D, how come?
Chlorine is bubbled at anode so it should be red and at anode colourless at cathode since it is hydrogen??! 2009 winter-paper 12

 

[snipex]

Well see, for cathode it is blue because sodiumchloride is concentrated , in other words sodium will replace hydrogen and take its place in cathode, for anode am not sure but I think it is colourless because when sodium ion bexome sodium, free chlorine ions combine to from chlorine as a result oh is attracted by anode.

 

[Muskan Achhpilia]

Chemistry-
For complete combustion, one molecule of an organic compound needs 8 molecules of oxygen.
What could the formula of this compound be?
A C5H11OH
B C6H9OH
C C6H11OH
D C6H12

Answer-B(Winter 2007 paper 1,Q11)

 

[snipex]

Well its just that you try each organic vompound with 8 molecules of oxygen and see if it will be balanced or not.