What is the number of nitrogen atoms in 60.0g of CO(NH2)2.
(RAM: H,1;C,12;N,14;O,16;Avogadro constant:6x10^23)
A 3X10^23
B 6x10^23
C 1.2x10^24
D 2.4x10^24
@Callisto

Question

anonymous · Answer

@dan815

somy · Answer

find mole 
mole = mass / molecular mass 
u have mass & molecular mass u can get using periodic table

somy · Answer

once u find mole 
multiply it by Avogadro's number

somy · Answer

& u'll get the answer

anonymous · Answer

my answer is C. @Somy

aaronandyson · Answer

You had asked this question 14 days back http://openstudy.com/study#/updates/54f2a546e4b006da7538b11c

anonymous · Answer

But the answer is wrong :(

somy · Answer

ah wait we are not done 
sorry i didnt notice the N part

somy · Answer

so you find the total mole and of that total mole you have to find mole of N

somy · Answer

show me your first part working 
mole finding 
with the answer

anonymous · Answer

okay

anonymous · Answer

$$CO(NH _{2})_{2}=60gmol^{-1}$$

anonymous · Answer

$$\frac{ 60g }{ 60gmol^{-1} }=1mol$$

somy · Answer

good now look 
1 mole  = whole compound molecular mass 
X mole = molecular mass of nitrogen

somy · Answer

X mole = 1 mole x molecular mass of nitrogen / molecular mass of the whole compound

somy · Answer

show me your next working using this

anonymous · Answer

okay

anonymous · Answer

$$1mol~\times2\times6\times10^{23}mol^{-1}=12\times10^{23}$$

anonymous · Answer

$$=1.2\times10^{24}$$

somy · Answer

no no, this current working 
good now look 
1 mole  = whole compound molecular mass 
X mole = molecular mass of nitrogen 
X mole = 1 mole x molecular mass of nitrogen / molecular mass of the whole compound

anonymous · Answer

$$=\frac{ 1mol~\times28gmol^{-1} }{ 60gmol^{-1} }$$

somy · Answer

yep

anonymous · Answer

$$=0.5mol$$

somy · Answer

now multiply by Avogadro constant

anonymous · Answer

$$=0.5mol~\times6\times10^{23}$$

somy · Answer

yep

anonymous · Answer

$$=3\times10^{23}$$

somy · Answer

yas! :3 
i hope its correct?

somy · Answer

coz if not than i'll be shocked lol

anonymous · Answer

Answer in the book say it is C.

somy · Answer

but C will be all atoms

somy · Answer

while q is asking for N atoms only

somy · Answer

i'll look through it again

anonymous · Answer

ok

somy · Answer

hmm you multiplied mole of the whole compound which was 1 mole by 2 
did u do it because there are two N atoms in a compound?

anonymous · Answer

yep

somy · Answer

got it sorry thats my error http://prntscr.com/6h2t1n (different q but you can get whats going on)

somy · Answer

there are 2 N atoms per molecule of  CO(NH2)2

somy · Answer

so we have to multiply by 2

somy · Answer

u are correct :) sorry had some errors in memory :D

anonymous · Answer

Thnx a lot @somy :)

somy · Answer

lol more like, thank you for refreshing my memory :)

anonymous · Answer

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