How many molecules are in 42.3g sample of water

The number of molecules is molecules

here we need to find out how many moles of water we have, water has molar mass of 18.015g/mol

Now  

= 2.3480 moles

Here we used avogadros number to find the number of molecules of water

= molecules

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The number of molecules is 1.4140*10^24 molecules

Explanation:

To know the number of molecules, we need to determine how many moles of water we have, water has molar mass of 18.015g/mol

This means that one mole of water molecules has a mass of 18.015g.

42.3g * 1 mole H2O/18.015g

= 2.3480 moles H2O

We are using avogadros number to find the number of molecules of water

2.3480 H2O * 6.022*10^ 23moles/ 1mole of H2O

That's 2.3480 multiplied by 6.022*10^23 divided by 1 mole of H2O

Number of molecules = 1.4140 *10^24 molecules

what are the choices?

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).