Question

How many molecules are contained in a 7.20-g sample of dimethylmercury?

Answer 1

Answer:

$1.88x10^{22}molecules (CH_3)_2Hg$

Explanation:

Hello,

Dimethylmercury: $(CH_3)_2Hg$ has a molecular mass of:

$M_{(CH_3)_2Hg}=12*2+1*6+200.59=230.6g/mol$

Now, the following mass-mole relationship including the Avogadro's number allows us to compute the requested molecules as follows:

$7.20g(CH_3)_2Hg*\frac{1mol(CH_3)_2Hg}{230.6g(CH_3)_2Hg} *\frac{6.022x10^{23}molecules (CH_3)_2Hg}{1mol(CH_3)_2Hg} =1.88x10^{22}molecules (CH_3)_2Hg$

Best regards.

Answer 2

The formula for dimethyl mercury is. HgC2H6 = (2x12) + (6x1) + (1x200.6) = 230.6 
So the molar mass of dimethyl mercury is 230.6 g/mol. 
Number of moles in 4.2g of dimethymercury = 4.2/ 230.6 = 0.0182 moles.  
1 moles of dimethymercury contains 6.02 * 10^23 
Hence 0.0182 moles contains X 
X = 0.0182 * 6.02 * 10^23 = 0.10952 * 10^23 = 1.0952 * 10^22.