Chemistry Mass of moles

I have a couple questions I need answered. Please show how you got the answer. I need to know how to do it as well as the answer.

1.) What is the mass of 8.96 moles of ammonia?

2.) What is the mass of 5.66 x 10^23 molecules of water?

3.) How many atoms are there in 45.9 grams of aluminum?

1) ok the formula for ammonia is NH3, so it is nitrogen + hydrogenx3

14+3=17 , 17 is the rmm for one mole of ammonia, so 17 x 8.96 =152.32

2) 5.66 x 10^23= 5660.
one mole of water is 18gmol-1
using avogadros constant, the mass of one mole of water in kilograms is:
0.00000000000000000000000002991507kg

times this by 5660 which is 2.991507 × 10-26kg x 5660 = 1.693192962 x 10^30


3) 10 grams aluminum (1 mole Al/26.98 grams)(6.022 × 1023/ 1 mole Al)

= 2.2 × 10^23 atoms of aluminum

divide this by 10, which is :
2.2 x 10^22 atoms in one gram

times this by 45.9 which is 1.0098 x 10^24 atoms in 45.9g of aluminium.

hope i helped :)

im not going to look up the numbers for you, but if you willing to learn you can do that yourself.. here how to solve these problems.


1. 8.96 moles NH3(molar mass NH3(17 g)/1 mole NH3 )=

multiply through and you get the answer...

2. 5.66E23 molecules H2O(6.02E23 moles H2O/1 molecule H2O)(18g H2O/1 mole)=


multiply through and you get the answer...


3. same procedure, use Avogadro number aqnd molar mass of Al