Measure out 0.210 moles of salt (NaCl) into a blue dry cup, you need to convert to mass in grams. Show work:

Question

I need work to be shown. I would also need help with these two questions. Put 2.85x10^23 molecules of water into a clear cup. You need to convert to mass in grams. Show work:

Answer 1

For the first question, you convert 0.210 moles of NaCl to grams by using the molar mass of NaCl which is the atomic mass of Na plus the atomic mass of Cl.  This is 22.99 + 35.45 = 58.44 g/mole = molar mass NaCl.

Grams of NaCl = 0.210 moles NaCl x 58.44 g NaCl/moles NaCl = 12.27 grams = 12.3 grams NaCl (3 sig. figs.)

 

For the second question, you convert 2.85x10²³ molecules of water to grams by first converting it to moles of water using Avogadro's number, and then converting the moles of water to grams of water using the molar mass of water (18 g/mole).

Grams water = 2.85x10²³ molecules x 1 mole/6.02x10²³ molecules x 18 grams/mole = 8.52 grams water (3 sig. figs.)