Physics, Chemistry and Biology: Post your doubts here!

[Muaaz Iqbal]

Hi Guys
In artifical selection Best varieties of Domestic Animal and Plants are chosen by man and are breed in order to improve thier "strain"
Question is What Does the Word "Strain" Mean ?

 

[sj0007]

Yes u can definitely write on those blank pages but u need to refer CLEARLY which question it is and which part

Thnx!!!!!!!!!!

 

[sj0007]

The difference between the mass is around 17.5 kg. And the difference between the years is 5. They've asked for the average.
17.5/5 = 3.5. Thus the answer is B.

Thnx alot!!!!!!!!!

 

[sj0007]

Hi Guys
In artifical selection Best varieties of Domestic Animal and Plants are chosen by man and are breed in order to improve thier "strain"
Question is What Does the Word "Strain" Mean ?

A strain is a population of organisms that descends from a single organism. Strains within a species may differ slightly from one another in many ways. Strains are often created in the laboratory by mutagenizing existing strains

Hope that clears ur doubt................

 

[Muaaz Iqbal]

Oh.. Thanks alot

A strain is a population of organisms that descends from a single organism. Strains within a species may differ slightly from one another in many ways. Strains are often created in the laboratory by mutagenizing existing strains

Hope that clears ur doubt................

Oh.. Thank's alot

 

[radzed]

Hello!
Can someone explain to me in brief what the anomalous behavior of water is all about?

 

[Saad the Paki]

A is the answer
because the hydrogen ions ( red litmus paper turns red due to the H+ ions which means its acidic at this part of the apparatus) will move towards the cathode where reduction occurs there and hydrogen gas is given off
since it is concentrated solution so chlorine ions will move towards the anode where oxidation will occur leaving behind sodium hydroxide which is a base and that's the reason y the litmus paper will turn blue at this part of the apparatus

Well... i thought abt that too but i just checked the mark scheme and answer is D..! WTF..?!

 

[sj0007]

Well... i thought abt that too but i just checked the mark scheme and answer is D..! WTF..?!

The answer is D cuz it is the electrolysis of concentrated aqueous sodium chloride.............................
Chlorine is formed at the anode, bleaches the litmus and causes it to become colourless and well I am not sure why it is blue on the cathode but since we know that the anode should be colourless, we can choose the option D

Hope that helps!!

 

[Mr.Physics]

Well... i thought abt that too but i just checked the mark scheme and answer is D..! WTF..?!

Yeah !! It's D and it's pretty simple !! H+ ions go towards cathode and gain electrons there to form H2 gas !! Cl- ions go towards anode because the solution is concentrated and they lose electrons to form Cl2 !! After sometime , at cathode, H+ ions get finished up because they all were converted into H2 gas after gaining electrons !! now here the OH- ions react with Na+ ions to form NaOH which is basic and turns litmus blue. At anode , Cl2 gas is formed which bleaches the litmus paper !!

 

[sj0007]

Can anyone tell me what the suck back effect is? Cuz I am confused a little.........................

 

[Saly Elkady]

Well... i thought abt that too but i just checked the mark scheme and answer is D..! WTF..?!

D
how ?

 

[masterex567]

D
how ?

I'm not sure of this answer, but in my opinion,
first of all hydrogen will be produced at the cathode, and chlorine at the anode. So at the anode, the chlorine will bleach the litmus paper, hence there is no color change in it after it is bleached. Hence colorless at the anode.
Next, at the cathode, hydrogen is produced which has no effect on litmus either and it escapes. What the litmus is left in is Sodium Hydroxide. Because out of sodium chloride solution, the hydrogen and chlorine have escaped therefore leaving only Na+ and OH- ions in solution. Hence, litmus will turn blue in contact with this sodium hydroxide left, since sodium hydroxide is basic and turns litmus blue!

 

[masterex567]

Guys can anyone help me with this chemistry question, with an explanation also.
Thank you!

 

[Saly Elkady]

I'm not sure of this answer, but in my opinion,
first of all hydrogen will be produced at the cathode, and chlorine at the anode. So at the anode, the chlorine will bleach the litmus paper, hence there is no color change in it after it is bleached. Hence colorless at the anode.
Next, at the cathode, hydrogen is produced which has no effect on litmus either and it escapes. What the litmus is left in is Sodium Hydroxide. Because out of sodium chloride solution, the hydrogen and chlorine have escaped therefore leaving only Na+ and OH- ions in solution. Hence, litmus will turn blue in contact with this sodium hydroxide left, since sodium hydroxide is basic and turns litmus blue!

i will make sure with my chemistry teacher and let uk
but give me the year and the varient of this paper

 

[Parmeen]

I am having problem with moments. Especially stable,neutral and unstable equilibrium..plx help!!!!!!!!!!

http://hgphysics.com/gph/c-forces/2-force-effects/1-moment/
this might help u

 

[Saad the Paki]

Guys can anyone help me with this chemistry question, with an explanation also.
Thank you!

%yield is practical yield/theoretical yield...
So to find theoretical yield we use the ratio method... if 250g were made by 80g,then how much will be made 4g...
4×250/80=12.5g... so % yield will be 11.5/12.5×100=92%
and the same way for the rest..
8×250/80=25.. 23.5/25×100=94%
12×250/80=37.5... 35/37.5×100=93.3%
16×250/80=50.... 46.5/50×100=93%
So answer is B

 

[Saad the Paki]

i will make sure with my chemistry teacher and let uk
but give me the year and the varient of this paper

Its O/N 12 paper 11 .. Q9.

 

[Saly Elkady]

Its O/N 12 paper 11 .. Q9.

ok thanks

 

[masterex567]

%yield is practical yield/theoretical yield...
So to find theoretical yield we use the ratio method... if 250g were made by 80g,then how much will be made 4g...
4×250/80=12.5g... so % yield will be 11.5/12.5×100=92%
and the same way for the rest..
8×250/80=25.. 23.5/25×100=94%
12×250/80=37.5... 35/37.5×100=93.3%
16×250/80=50.... 46.5/50×100=93%
So answer is B

Thank you!

Please help me in this one also:

 

[Saly Elkady]

Thank you!

Please help me in this one also:

A is the answer
500/24=20.8333...
20.833*4/5 =16.677...
16.677... * 24= 400 cm3