Physics, Chemistry and Biology: Post your doubts here!

[Naman17]

Please some one help me with this problem. .. i have exam tomorrow
On the following question answer in mark scheme is 9.5.. but mine is coming exact 9

Your image is printed on a smaller scale, maybe becoz of the margins

 

[sohaib ul haq]

Can some one help me out with this? What can be the answer and why?View attachment 51656

ans is C

this whole thing is placed on an plastic support so as their is no connection to the earth electron cant go to earth resulting in a shock to any one who touched it

 

[Saad the Paki]

ans is C

this whole thing is placed on an plastic support so as their is no connection to the earth electron cant go to earth resulting in a shock to any one who touched it

Well if someone will recieve a shock doesnt that mean there is an electric current in the case thus causing the shock.?! And that makes the answer A

 

[masterex567]

Thank you so much man. Are you giving the board exam for IGCSE Physics in M/J 2015? I have some doubts maybe we could help each other? Just sayin'

Yes, i am.
And sure definitely! Feel free please!

Hi.. Can u please let me know that from where did u get access to the 2014 examiner's report..?! Please..!

onlineexamhelp.com

 

[Mr.Physics]

Hey can any one explain "sacrificial protection" ??

 

[Saad the Paki]

Hey can any one explain "sacrificial protection" ??

A less reactive metal (iron) is coated with a more reactive metal (zinc)
This is when a more reactive metal 'sacrifices' its electrons...
So basically the more reactive metal loses electrons instead of the object coated (iron for example)
Since loss of electrons (oxidation) is essential for rusting... Iron will not lose electrons at all since the more reactive metal is doing that.. so it will not rust

 

[Saad the Paki]

Can someone help me with this..!
A,B & D all seem correct answers but apparently the ans is B..!
Can someone please explain why..!

 

[Lola_sweet]

Can someone help me with this..!
A,B & D all seem correct answers but apparently the ans is B..!
Can someone please explain why..!

Glowing splint only works for oxygen
Limewater only for CO2
here they want a test for all 3 gases
and u knw lighted splint extinguishes in CO2 and makes pop sound in H2
So best answer is B

 

[Saad the Paki]

Glowing splint only works for oxygen
Limewater only for CO2
here they want a test for all 3 gases
and u knw lighted splint extinguishes in CO2 and makes pop sound in H2
So best answer is B

Oh wow.... thanks..! ^_^

 

[Lola_sweet]

Oh wow.... thanks..! ^_^

U r welcome

 

[sj0007]

1. First you need to find the dot R (Q10 a i) which is the same distance from surface on other side as S is.
2. Now put your compass on S, and complete the three circles to the other side of the surface.
3. Now place your compass on R, and try to complete a circle from the circular wavefronts drawn on the right hand side to make a circle on this left hand side.
4. Repeat instruction in 3, to complete circles from right hand side to left hand side, from compass on R for all three wavefronts.
5. After its drawn, erase the circles on right hand side of reflecting surface leaving ones drawn on the left hand side.

There you go, ask if you need any clarification with above.

I just saw ur reply today...........thanx a lot!!!!!!!!!!! That explanation just cleared everything!!!!!!!!!

 

[sj0007]

I also wanted to ask that u can not write or continue your answer in the blank space below the question, right?
So if anything like this happens we use the blank pages, right?

 

[sj0007]

Does anybody know how the answer to Q29 is A????

 

[Saad the Paki]

I also wanted to ask that u can not write or continue your answer in the blank space below the question, right?
So if anything like this happens we use the blank pages, right?

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

 

[AnonymousX9]

Does anybody know how the answer to Q29 is A????

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.

 

[Nada Hafsah]

Could you guys please help me with this question? Why is it D?

 

[AnonymousX9]

It's D because the element with the proton number 37 is Rubidium which forms a singly charged positive ion (+1 charge) in it's compounds/salts.

 

[Saad the Paki]

Can some one tell me what the answer is and why? I'd Appreciate it

 

[Saly Elkady]

Can some one tell me what the answer is and why? I'd Appreciate it

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

 

[Nada Hafsah]

It's D because the element with the proton number 37 is Rubidium which forms a singly charged positive ion (+1 charge) in it's compounds/salts.

Thank you soo much