Which of the following molecules has the largest mass?

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Which of the following molecules has the largest mass?

Can someone explain to me how to do question 62? Thanks!

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Answer 1 · 2017-03-17T23:47:47

The answer is ${A) 1.5 moles O}_{2}$ $"A) 1.5 moles O"_2$

Explanation:

For starters, you know that diatomic oxygen, $O_{2}$ $"O"_2$ , has a molar mass equal to

$M_{{M O}_{2}} = {32.0 g mol}^{- 1}$ $M_ ("M O"_2) = "32.0 g mol"^(-1)$

Now, each molecule of oxygen contains $2$ $2$ atoms of oxygen, so right from the start, you can say that $1$ $1$ mole of oxygen atoms will have a molar mass that is equal to half of the molar mass of diatomic oxygen

$M_{M O} = {16.0 g mol}^{- 1}$ $M_ ("M O") = "16.0 g mol"^(-1)$

So, if $1$ $1$ mole of oxygen molecules has a mass of $32.0 g$ $"32.0 g"$ , it follows that you will get $\frac{1}{2}$ $1/2$ moles of oxygen molecules in $16.0 g$ $"16.0 g"$ of $O_{2}$ $"O"_2$ .

Therefore, you can say that

${16 g O}_{2} = \frac{1}{2} . {moles O}_{2}$ $"16 g O"_2 = 1/2color(white)(.)"moles O"_2$

You can use the fact that each oxygen molecule contains $2$ $2$ atoms of oxygen to say that $1.24 \cdot 10^{24}$ $1.24 * 10^(24)$ atoms of oxygen will be equivalent to $\frac{1}{2} \cdot 1.24 \cdot 10^{24}$ $1/2 * 1.24 * 10^(24)$ molecules of oxygen.

Therefore, you have

$1.24 \cdot 10^{24} . atoms O = 6.20 \cdot 10^{23} . {molecules O}_{2}$ $1.24 * 10^(24)color(white)(.)"atoms O" = 6.20 * 10^(23)color(white)(.)"molecules O"_2$

Finally, you know that $1$ $1$ mole of a molecular substance must contain $6.022 \cdot 10^{23}$ $6.022 * 10^(23)$ molecules of that substance.

This means that the samples you have at point $C$ $"C"$ and $D$ $"D"$ will be equivalent to a little less than $1$ $1$ mole of oxygen molecules

$6.20 * 10^(23)color(red)(cancel(color(black)("molecules O"_2))) * "1 mole O"_2/(6.022 * 10^(23)color(red)(cancel(color(black)("molecules O"_2))))$

$= 6.20/6.022 color(white)(.)"moles O"_2$

and

$6.06 * 10^(23)color(red)(cancel(color(black)("molecules O"_2))) * "1 mole O"_2/(6.022 * 10^(23)color(red)(cancel(color(black)("molecules O"_2))))$

$= 6.06/6.022 color(white)(.)"moles O"_2$

You can now say that the four samples contain

$"A: " "1.5 moles O"_2$

$"B: " "0.5 moles O"_2$

$"C: " 6.20/6.022color(white)(.)"moles O"_2$

$"D: " 6.06/6.022 color(white)(.)"moles O"_2$

Therefore, sample $"A"$ will have the larger mass because it contains the biggest number of oxygen molecules.

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Which of the following molecules has the largest mass?

Can someone explain to me how to do question 62? Thanks!

1 Answer

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