Physics, Chemistry and Biology: Post your doubts here!

[SREYAh]

give a reason for each of the following statements
a) Before using an indicator paper to test for ammonia, the paper should be moistened with water. (why)
b) if an aqueous solution is known to contain either Al(3+) aqueous or Zn(2+) aqueous , addition of aqueous ammonia will show which ion is present.
c) when testing for chloride, the solution should be acidified with dilute nitric acid before either aqueous silver nitrate or aqueous lead(II)nitrate is added.
[ 6 marks]
please help me....i will be very grateful to you...pleaseeee...

 

[SREYAh]

give a reason for each of the following statements
a) Before using an indicator paper to test for ammonia, the paper should be moistened with water. (why)
b) if an aqueous solution is known to contain either Al(3+) aqueous or Zn(2+) aqueous , addition of aqueous ammonia will show which ion is present.
c) when testing for chloride, the solution should be acidified with dilute nitric acid before either aqueous silver nitrate or aqueous lead(II)nitrate is added.
[ 6 marks]
please help me....i will be very grateful to you...pleaseeee...

 

[Faheen]

give a reason for each of the following statements
a) Before using an indicator paper to test for ammonia, the paper should be moistened with water. (why)
b) if an aqueous solution is known to contain either Al(3+) aqueous or Zn(2+) aqueous , addition of aqueous ammonia will show which ion is present.
c) when testing for chloride, the solution should be acidified with dilute nitric acid before either aqueous silver nitrate or aqueous lead(II)nitrate is added.
[ 6 marks]
please help me....i will be very grateful to you...pleaseeee...

a)im not sure but i think because it is the OH- IONS that cause the solution to be alkaline which are only produced when ammonia dissloves in water hance damp litmus paper is used
b)because with sodium hydroxide both the ions produce a white precipiatate that is soluble in excess to give a colourless solution wile with aqueous ammonia al(3+) ions produce a white precipitate that is insoluble in exxccess but zn(2+) ions produce a white precipitate that is soluble in excess to give colourless solution.
c)to remove/dissolve any carbonates present in the solution.
hope it helps

 

[MariamIqbal]

Assalam-o-Alaikum.
Post your Physics, Chemistry and Biology doubts in here and members, along with me will try their best to help you out.

Can I find Biology's 'classified' past papers anywhere online?

 

[SREYAh]

a)im not sure but i think because it is the OH- IONS that cause the solution to be alkaline which are only produced when ammonia dissloves in water hance damp litmus paper is used
b)because with sodium hydroxide both the ions produce a white precipiatate that is soluble in excess to give a colourless solution wile with aqueous ammonia al(3+) ions produce a white precipitate that is insoluble in exxccess but zn(2+) ions produce a white precipitate that is soluble in excess to give colourless solution.
c)to remove/dissolve any carbonates present in the solution.
hope it helps

oh...thank you so much dear...
you are very generous...:*

 

[Mackintosh]

Can anyone please tell me where Vertebrates classification is there in our syllabus coz i have a little doubt on it, whether its there or not? not mentioned in the syllabus? wat abt u guys?

 

[Tiffygirly]

You guys do u have a revision/studyguide for Chemistry and Physics? Please,I need it

 

[johnsternater2000]

You guys do u have a revision/studyguide for Chemistry and Physics? Please,I need it

Haz dis:
all rights to respective authors

 

[shazmina]

Can anyone please tell me where Vertebrates classification is there in our syllabus coz i have a little doubt on it, whether its there or not? not mentioned in the syllabus? wat abt u guys?

yesh its there

 

[Mackintosh]

yesh its there

But its not mentioned in the syllabus issued by the Cambridge..btw thanks!

 

[shazmina]

But its not mentioned in the syllabus issued by the Cambridge..btw thanks!

well yea it isnt mentioned ... but its bettr to study and it is imp
nd ur welcome

 

[Mackintosh]

Can I find Biology's 'classified' past papers anywhere online?

Unfortunately no if u reside in Jeddah there is a probability in Afnan or Jarir bookstore...

 

[Al-Anoud]

Do we answer AS paper-2 (experimental questions) exactly like the IGCSE p-6 questions?

 

[Lanocaster]

Hey bro,
Can you please explain transistor potential dividers to me? I know how a potential divider works but I am not able to understand how the position of the thermistor/LDR affects the transistor. Diagrams show that the thermistor/LDR must be placed on the side where the emitter of the transistor is, but why?
Thanks in advance
Lanocaster

 

[Power_PC]

Hey guys I need some help! ASAP. Can you guys tell me some tips and tricks for IGCSE Physics (0625) EXTENDED, and what topics to prepare for paper 6 (61 : Practical). Gosh im freakin' out aloot!!! :S paper 6 is on 12th :S

 

[Al-Anoud]

^^Does anyone have the CD for this?

 

[Mackintosh]

Hey guys I need some help! ASAP. Can you guys tell me some tips and tricks for IGCSE Physics (0625) EXTENDED, and what topics to prepare for paper 6 (61 : Practical). Gosh im freakin' out aloot!!! :S paper 6 is on 12th :S

Sorry no a physics student well u could try some of these

http://g2physics.wikispaces.com/file/view/EXAMINER+TIPS+FOR+IGCSE+PHYSICS+0625+(S04).pdf

 

[Saket Sekhsaria]

Can someone help in Question Number 9, Summer 2009 in Chemistry paper 3.
And also why Temperature supports the backward reaction like in the graph Q6 (b)

 

[johnsternater2000]

Hey guys I need some help! ASAP. Can you guys tell me some tips and tricks for IGCSE Physics (0625) EXTENDED, and what topics to prepare for paper 6 (61 : Practical). Gosh im freakin' out aloot!!! :S paper 6 is on 12th :S

for physics ATP know how to: (prepare, as this list is extremely hard and only for people who know how to do proper physics...)
Know how to measure ( i can almost gaurentee you 5-15 marks by just being able to measure the leangth of something or reading off values!)
Know how to draw- you don't need to be picasso (although i don't think you would get any marks for drawing in the exam in his style see http://timenewsfeed.files.wordpress.com/2011/07/picasso-drawing.jpg?w=455&h=320&crop=1) but you do need to know how to draw a straight line (i.e be able to use a ruler, which) and follow instuctions. Most will be drawing an electrical diagram or something to do with the refraction of light.
know what the parallax error is and how to avoid it- take reading prependicular to the scale, ruler, thermometer, whatever.
calculate something when they give you the formula (WOW thats soooo.... hard)
know what variables to control in an experiment
be able to draw a graph (inc line of best fit and the right scales, don't use scale breaks unless specifically allowed, just start the scale from a reasonable number instead of zero)

most common topics in physics atp: lenses, themometers,refraction (especially with optical pins,) Hookes law etc

 

[Tiffygirly]

You guys reactivity series for cations and anions. Can anyone list it for me,for cations,from least to most reactive,and also for anions. Pleasee,thanks xxx