Biology; Chemistry; Physics: Post your doubts here!

[peacce]

haaaaaaaaaaaaaaann dekha nhi

 

[peacce]

mass percentage = (total mr of that element/total mr of compound) * 100

hey do quote the msg dhundna mshkil hjata hai

 

[peacce]

how is it A?

 

[Awesome12]

how is it A?

H2 gas will be formed that will be released reducing the mass of the beaker.
However the beaker has its own mass and the total mass will not decrease to 0

 

[Mahnoorfatima]

K+ and H+ won't do anything with NaOH. Fe+2 gives a green ppt and Ca+2 gives white ppt.

I know that but if you check the ms they've written something about ca2+ not dissolving in excess.

 

[peacce]

xplain xpainnnn
Ans is D

 

[peacce]

H2 gas will be formed that will be released reducing the mass of the beaker.
However the beaker has its own mass and the total mass will not decrease to 0

idun understnd

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w08_qp_1.pdf
Question 19 anyone?

 

[Abdul Hanan]

idun understnd

the reaction will be:
CaCO3+HCL=CaCl2+H2O+CO2
carbon dioxide escapes the container....
other products remain inside
leading to overall decrease in mass
caco3 is marble
first there are more particles so faster decrease initially then slower

 

[kirann]

how its done plz show the working

 

[DaniyalK]

I know that but if you check the ms they've written something about ca2+ not dissolving in excess.

There are 3 marks. 1 for Greent ppt. 1 for saying it's iron hydroxide and the last one for white ppt. Saying the white ppt dissolves is wrong because it doesn't.

 

[Abdul Hanan]

how its done plz show the working
View attachment 43303

answer ?

 

[kirann]

answer ?

c

 

[DaniyalK]

how its done plz show the working
View attachment 43303

Zinc is more reactive than copper so it will displace copper. The products will be Copper + Zinc Sulphate.

 

[Abdul Hanan]

c

ok... this is a displacement reaction
Zn+CuSO4=ZnSO4+Cu
here zinc looses electrons so it is oxidised.....
(ZnSO4 ppt. not formed as it is soluble)

 

[Fate0]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_1.pdf
Question 19 anyone?

Combine the Equations .
You get the mol ratio of NH3 to mol ratio of fertiliser as 2:1.
Mass of NH3 = 17 tonnes
Moles of 17 tonnes of NH3 = 17 x 10^6 / 17 = 1 000 000
Moles of fertilisers = 500000 mol
Mass = mol x MR
500000 x 80 = 40 tonnes

 

[kirann]

Zinc is more reactive than copper so it will displace copper. The products will be Copper + Zinc Sulphate.

the answer is c im confused b/w oxidation and reduction

 

[Lilly2318]

yep.. agr summary mei word limit exceed hjai tu kia hta man i exceeded ittttttttttttttttt

dont worry much. read latest ms. u'll get ur anser

 

[DaniyalK]

the answer is c im confused b/w oxidation and reduction

Originally, zinc has a charge of 0. When it forms zinc sulphate, the charge on zinc is +2. Increase in charge means oxidation.

 

[kirann]

ok... this is a displacement reaction
Zn+CuSO4=ZnSO4+Cu
here zinc looses electrons so it is oxidised.....
(ZnSO4 ppt. not formed as it is soluble)

umm, if electrons are higher in the product than reactants then oxidation and if its negative then reduction?