Physics, Chemistry and Biology: Post your doubts here!

[Knightmare11]

wat abt hexane ..... wat is d test 4 tat

For hexane, use the 'diffusion' test using Iodine.
In a test tube, put some Hexane and Aqeous Iodine. The Iodine is non-polar whereas Hexane is polar.So they are immiscible; Moreover Iodine is reddish brown (aqeous) but forms a purple layer layer with hexane as it diffuses

2nd test:
Combustion - Alkanes burn to give Co2 + H2O

3rd test:
Alkane or alkene?!

Use bromine in a absence of uv --> Alkane (Hexane) stays same Alkene (Hexene) decolorises

 

[Counter Logic Gamer]

Sulfur and carbon oxides such as sulfur dioxide and carbon dioxide are acidic and the litmus paper would not turn blue.
Iodine does not form a white solid oxide , and from lab experience we know that calcium oxide is white and since all metal oxides are basic (turn litmus blue) we can say the answer must be A calcium oxide as it is the only option that fits it

Thank you guys for helping me even it was a bit late(after my xams)i would express my gratitude by thanking you from the bottom of my heart!! Keep It UP!! Good Work Benifits Others and Everyone!!

 

[suri003]

tank

For hexane, use the 'diffusion' test using Iodine.
In a test tube, put some Hexane and Aqeous Iodine. The Iodine is non-polar whereas Hexane is polar.So they are immiscible; Moreover Iodine is reddish brown (aqeous) but forms a purple layer layer with hexane as it diffuses

2nd test:
Combustion - Alkanes burn to give Co2 + H2O

3rd test:
Alkane or alkene?!

Use bromine in a absence of uv --> Alkane (Hexane) stays same Alkene (Hexene) decolorises

thanku....................

 

[Counter Logic Gamer]

40 The diagram shows an area being developed for industry and agriculture.

trees being cut down to
provide agricultural land
fertilisers, herbicides and
pesticides applied to the land
lake
smoke containing
sulphur dioxide
factory


Which would be the most likely to cause an initial increase in plant life in the lake?
A fertilisers
B herbicides
C pesticides
D smoke

 

[Kushal lodha 5336]

can someone tell me where can i find notes on d topic Organic Chemistry...........???
i find it really difficult................

 

[Zeeshan007]

What is the main function of muscle?
A absorption
B conduction
C contraction
D transport
whats conduction in B,?i knnow the right answer but just wondering what conduction is

The release of Ca2+, after receiving the nerve impulse, liberates the myosin's binding site on actin filaments. This enables a contraction, and a return of the calcium in the sarcoplasmic reticulum allows the muscle to relax.
More to the point I also read that calcium is a factor that can cause cramp.

 

[Zeeshan007]

40 The diagram shows an area being developed for industry and agriculture.

trees being cut down to
provide agricultural land
fertilisers, herbicides and
pesticides applied to the land
lake
smoke containing
sulphur dioxide
factory


Which would be the most likely to cause an initial increase in plant life in the lake?
A fertilisers
B herbicides
C pesticides
D smoke

A

 

[suri003]

can someone tell me where can i find notes on d topic Organic Chemistry...........???
i find it really difficult................

 

[Tiffygirly]

I need help on what to study for IGCSE Biology Paper 6 . Is there a textbook that is mainly for practicals,I haven't seen any

 

[Batrisyia]

Anyone has some notes on 'improvements and precautions' stuff of bio p6? Need to review on that. Thanks!

 

[Kdown567]

I need help on what to study for IGCSE Biology Paper 6 . Is there a textbook that is mainly for practicals,I haven't seen any

Anyone has some notes on 'improvements and precautions' stuff of bio p6? Need to review on that. Thanks!

Might help

https://www.xtremepapers.com/community/attachments/biology-igcse-experiments-docx.32480/

 

[Sudhanshu]

CAN ANYONE TELL ME THE DIFFERENCE BETWEEN ACCURACY AND RELIABILITY IN EXPERIMENTS??????
Eg; why was the experiment repeated 3 times ?? Is it to increase reliability accuracy or both???? Really Confused!!!!!!!

 

[suri003]

CAN ANYONE TELL ME THE DIFFERENCE BETWEEN ACCURACY AND RELIABILITY IN EXPERIMENTS??????
Eg; why was the experiment repeated 3 times ?? Is it to increase reliability accuracy or both???? Really Confused!!!!!!!

d experiment was reapeted to get a accurate result as if it was done 3 times ten d mean is taken out so if ter is any manual error or any kind of error is one of reading it wud be negligible ..................... hope so .............. am i right ?

 

[johnsternater2000]

CAN ANYONE TELL ME THE DIFFERENCE BETWEEN ACCURACY AND RELIABILITY IN EXPERIMENTS??????
Eg; why was the experiment repeated 3 times ?? Is it to increase reliability accuracy or both???? Really Confused!!!!!!!

I tink that you increase both because reliability means that if someone else repeats your experiments then they get the same results and accuracy is how close your conculsion was to the actual value. But you can repeat the same experiment and continously get the wrong result (maybe due to an error or bad apparatus.) When i looked in the past papers, the answers said "repeats to increase reliability" or something similar to that so i would just mention that we repeat the experiment to increase reliability.

 

[Sudhanshu]

Can anyone help me out in this tricky one, I really dont understand Stoichiometry can anyone explain the concept of doing similar problems.....
The percentage composition of a gaseous hydrocarbon is 85.62% Carbon and 14.38% Hydrogen.
The density of this gas is 1.26g / dm3 (litre) at NTP (where volume of one mole of gas is 24dm3).
Determine the molecular formula of the hydrocarbon.

Well if you want something more challenging here's more:


Thanks for your help!

 

[Sudhanshu]

Well one more.............
Find the current through the 15 Ohms Resistor in the circuit.......

 

[suri003]

Well one more.............
Find the current through the 15 Ohms Resistor in the circuit.......
View attachment 32490

welll idk if m right
V=IR...so I=V/R...so v=55n R=15....
::.. 55/15=3.7
wats d answer any idea /?

 

[Sudhanshu]

welll idk if m right
V=IR...so I=V/R...so v=55n R=15....
::.. 55/15=3.7
wats d answer any idea /?

Well evn I dont know But seeing so many resistors around it in series and parallel connection I think there's more to it isnt''ít.....
BTW will you solve the Chemistry Question from my earlier post. My main doubt is in first one Hydrocarbons.The rest are tricky these are not so urgent..............
Anyways A BIG THANKS FOR TRYING............

 

[suri003]

Well evn I dont know But seeing so many resistors around it in series and parallel connection I think there's more to it isnt''ít.....
BTW will you solve the Chemistry Question from my earlier post. My main doubt is in first one Hydrocarbons.The rest are tricky these are not so urgent..............
Anyways A BIG THANKS FOR TRYING............

i guess when tey hv asked for tat resistor so u lll find out of tat itself na ...
do u hv d answer for d hydrocarbon one coz i hv solved it m really bt sure abt it coz i got it easily heh

 

[Sudhanshu]

I will post it as soon as

i guess when tey hv asked for tat resistor so u lll find out of tat itself na ...
do u hv d answer for d hydrocarbon one coz i hv solved it m really bt sure abt it coz i got it easily heh

I get it Cos Sadly I dont have an MS for these qquestions...............................
Do you have any friends on XPC or in real, who could do it then please ask them to help me too..........