Can I ask why 41 answer is B?The chemical formula of vinegar is CH3COOH.The product between vinegar and calcium carbonate is (CH3COO)2Ca+CO2+H2O.Soap will form scum in the presence of calcim ion.
calcium carbonate is an insoluble salt,we cannot wash it with soap unless you scratch it.We use vineger to react and produce soluble (CH3COO)2Ca.From the question,“in order to remove the white layer”,so don't think too much about which is suitable to wash with soap.
For number 23, the question ask which of the following will produce the least gas bubbles. If copper we to react HCl, well, they be no reaction and therefore no bubbles. I guess my overall question is : Is no gas bubbles considered as least gas bubbles?
No, HCl acid does not react with copper. Only those metals whose standard reduction potentials are lower than that of hydrogen react with non-oxidising acids like HCl and dil.H2SO4, and displace hydrogen from them. Copper has higher reduction potential (more positive) than hydrogen, and it does not react with HCl acid.
Thank you very much
ReplyDeleteThanks but I had finished all my papers. :)
ReplyDeleteCan I ask why 41 answer is B?The chemical formula of vinegar is CH3COOH.The product between vinegar and calcium carbonate is (CH3COO)2Ca+CO2+H2O.Soap will form scum in the presence of calcim ion.
ReplyDeletecalcium carbonate is an insoluble salt,we cannot wash it with soap unless you scratch it.We use vineger to react and produce soluble (CH3COO)2Ca.From the question,“in order to remove the white layer”,so don't think too much about which is suitable to wash with soap.
DeleteFor number 23, the question ask which of the following will produce the least gas bubbles. If copper we to react HCl, well, they be no reaction and therefore no bubbles. I guess my overall question is : Is no gas bubbles considered as least gas bubbles?
ReplyDeleteThis comment has been removed by the author.
DeleteWhy is no.23 B? Copper is lower than hydrogen in ecs. Thus it cannot displace hydrogen and no reaction occur isn't?
ReplyDeleteYup...totally true
DeleteNo, HCl acid does not react with copper. Only those metals whose standard reduction potentials are lower than that of hydrogen react with non-oxidising acids like HCl and dil.H2SO4, and displace hydrogen from them. Copper has higher reduction potential (more positive) than hydrogen, and it does not react with HCl acid.
ReplyDeletewhy 50 is A
ReplyDeleteI got 45 from this scheme
ReplyDeleteSir can i get spm 2016 answer scheme for mathematics,physics,biology and chemistry.
ReplyDeleteSir how to calculate the question 44 i cant get it ...
ReplyDeletethe cathode carbon is at the left...(4.0g)
Deleteyou should now that at the cathode cu is form
cu^2+ +2e^--->cu
1.find the no of mol of solution
2.find the weight by multiplying the mol of solution and the RAM of cu then you will get 1.6g
then 4.0g+1.6g=5.6g
note:carbon electrode is an inert electrode and does not take part in a chemical reaction but the brown solid form will stick at the cathode