You have 1.20 x 10 24 molecules of H2O. What is the mass of this sample?

Explanation:

In this case, we have to remember that relationship between the avogadro's number and the "mol" concept:

With this in mind, we can do the first conversion:

Now, if we calculate the molar mass of . The atomic mass of O is 16 g/mol and the atomic mass of H is 1 g/mol, so:

(16*1)+(1*2)= 18 g/mol

In other words, , so:

I hope it helps!

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explanation: