Stoichiometry?

Question

Stoichiometry?
i need help with this topic. i'm kinda new to this one. pls show some working as well so that i can learn from there thks.


1) how many moles are there in 8 grams of hydrogen gas?
2)how many moles are there in 8 grams of bromine liquid?
3)how many grams of neon have the same number of atoms as 8 grams of oxygen?

Answer 1

you just need to do cancellation... like

in #1 you need to leave moles/molecules...
start with the given and look for values you can use to cancel and be left with what is asked
*hydrogen =1g/mol..(molar mass).. you can invert it so that you could cancel...

mole of H= 8 grams*mol/g
mol of H=8 molecules


#2 just multiply the given with the molar mass of bromine liquid.

#3 Ne=20 g/mol ...... O=16 g/mol
gNe= 8 grams oxygen*1 mol oxygen/ 16 grams oxygen*20 g Ne/ mol Ne

gNe=10 g Ne

Answer 2

1) The hydrogen gas has the formula H2 (and not H since the molecule of hydrogen has 2 atoms!!!) So, the molecular weight of H2 is 2 grams and 8 grams correspond to 8/2 = 4 moles

2) Bromine has two atoms in the molecule of liquid. so ,the molecular weight of Br2 is 160. And 8 g = 8/160 = 0.05 moles

3) See question 1) 8 g of hydrogen = 4 moles
to have 4 moles of bromine you must have 4*160 = 640 grams

Answer 3

1)0.13 moles

2)9.99 moles
3) 8 gm oxygen is 1.99 moles. neon is 20.1797 g/mole....so you need 10.14 gm of neon