chemistry MCQs

[insomniac]

aint it C...???

 

[insomniac]

(45/50)*100= 90%

 

[CaptainDanger]

It is C... 90 %

 

[intelnehalem]

It is C (45/50 *100)

 

[izzahzainab]

but they say that the impurity is "below" copper in the reactivity series. that means that the 45 g deposit was of impurity. so the sample must be very impure: should be 5/45 *100 ????

 

[abcde]

http://www.xtremepapers.me/CIE/index.php?dir=Cambridge%20O%20Levels/5070%20-%20Chemistry/&file=5070_s08_qp_1.pdf

check question 12

It's C. To calculate the percentage purity you perform this calculation = 45/50 x 100% = 90%

 

[abcde]

but they say that the impurity is "below" copper in the reactivity series. that means that the 45 g deposit was of impurity. so the sample must be very impure: should be 5/45 *100 ????

Remember this fact always: during the electrolytic purification of copper, only copper is deposited at the cathode. The impurity collects at the bottom of the electrolytic cell to form an anode slime. So the gain in mass at the cathode is because of copper being deposited there.