## Nikhil619 2 years ago An alloy has Fe, Co , Mo in a composition of 71%, 12%, 17% respectively. How many cobalt atoms are there in a cylinder of radius 2.5 cm and length 10 cm .The density of the alloy is 8.2 g/ml.[At.wt Co=59]

1. shubhamsrg

mass= density * volume density is given volume = pi r^2 h fine mass 12% of mass is the final answer use appropriate units.

2. shubhamsrg

find*

3. Nikhil619

oh.. we should take v of cylinder as volume?

4. shubhamsrg

yep

5. Nikhil619

and they've asked number of cobalt atoms..how is that 12% of mass?

6. shubhamsrg

ahh okay 12% of that = mass of cobalt atoms in 1 mole of cobalt = avagadros no. atoms in given mass = ?

7. Nikhil619

12 % of that? what is that? no.of atoms? or no.of moles?

8. Peter14

looks like 12% by mass

9. shubhamsrg

12% of that , that'll give mass of cobalt in the compound

10. Nikhil619

what is 'that'?

11. Peter14

"that" is the mass of the cylinder I think

12. shubhamsrg

that is mass of the compound in the given volume -_-

13. Nikhil619

ok so mass of the alloy..right?

14. shubhamsrg

yo B|

15. Nikhil619

look..im sorry if u feel im dumb..but hw am i supposed 2 find mass of alloy?

16. shubhamsrg

mass = density * volume -_-

17. Nikhil619

Volume? again volume of cylinder?

18. Peter14

19. Nikhil619

@ Peter14 I KNOW THAT...im askin if volume of alloy is same as volume of cylinder..

20. Peter14

yes, because the alloy is in the shape of the cylinder

21. shubhamsrg

the allow is in in the cylinder, so there volumes must be equated

22. Nikhil619

oh ok...k i got this..i have 2 more...can i post them now??

23. Peter14

sure shub, you take one, i'll take the other

24. shubhamsrg

lol.. :D (Y)

25. Nikhil619

dont worry i can only post one-by-one...

26. Peter14

27. Nikhil619

One-by-one is easier for me..one itself is hard to understand..2 means gone!

28. Peter14

ok, that works