1. 2 moles He* 6.02 X 10²³ molecules/mole= 1.2 X 10²⁴ molecules (sometimes the word molecule can be used for a monoatomic substance)

2. 250 g H₂O(mole/18) = 13.8888 moles

13.8888 moles * 6.02 X 10²³ molecules/mole = 8.36 X 10²⁴ molecules

3. 32 g/6.02 X 10²³ molecules =5.31 X 10^-23 g/molecule

4. a)30 moles H₂O(1 O₂/2 H₂O) = 15 moles of O₂

15 moles of O₂* 6.02 X 10²³ molecules/mole =9.03 X 10²⁴ molecules

b) 40.0 g(mole/2g) = 20 moles H₂

ratio is 1:1, 20 moles H₂O

20 moles H₂O* 6.02 X 10²³ molecules/mole =1.205 X 10²⁵ molecules

5.

mass	moles	molecules
75 g H2O	=75/18 = 4.16666
23 g C12H22O11	=23/342= 0.067
1 g protein	=1/13 600= 7.35X10^-5
Doesn’t add up to 100 due to rounding
total	4.23399	=4.23399*6.02 X 10^23 = 2.55 X 10^24