Question

if you burn 51.0g of hydrogen and produce 450g of water, how much oxygen reacted

Answer 1

Reaction of water formation is

2H_2(g) + O_2(g) 2H₂O_(g)

2 mole of hydrogen is reacting with 1 mole of oxygen to form 2 moles of water

2 moles of hydrogen = 1.01 x 2 = 2.02 g

1 mole of oxygen = 32.00 g

1 mole of H₂O = 18 g

so

51 g of hydrogens means 51 /2.02 = 25.24 moles

reacting with

450 g of water = 450 / 18 = 25 moles   

so its almos seen that when 2 moles of hydrogen reacting with 1 mole of oxygen it forms 2 moles of water

so

moles of oxygen = 25/2 = 12.5 moles ( half moles of present hydogen and water moles)

so

12.5 moles of oxygen = 12.5 x 32 g

= 400g