1.
[tex]1.20 \: mol \times \frac{6.02 \times {10}^{23} }{1 \: mol} = 7.224 \times {10}^{23} atoms[/tex]
2.
[tex]9.25 \times {10}^{25 \:} molecules \times \frac{1 \: mol}{6.02 \times {10}^{23} } [/tex]
[tex] = 153.654485 \: moles[/tex]
3.
molar mass = 3(24.31) + 127.60 + 5(32.07)
molar mass = 360.88 g
4.
molar mass = 3(58.93) + 2(30.97) + 8(16.00)
molar mass = 366.73 g
5.
molar mass = 98.09
[tex]125 \: g \times \frac{1 \: mol}{98.09 \: g} = 1.274339892 \: moles[/tex]
//
I'm too lazy to do the rest but you should get a general idea of how to do it.
Also, round as you wish!
