Question

Sodium reacts with oxygen to produce sodium oxide. 4Na(s)+O2(g)→2Na2O(s).If you have 18.9 g of Na, how many grams of O2 are required for reaction?

Answer 1

4Na(s)+O2(g)→2Na2O(s)

From the above balanced equation 4 moles of Na reacts with 1 mole of O2

now we have to calculate no. of moles of Na
no. of moles of Na = (wt. of Na/atomic wt. of Na) = (18.9/23) = 0.822 moles

For 4 moles of Na ..........1mole of O2 requires
    0.822 moles of Na .......?
       = 1*0.822/4 = 0.205 moles

0.822 moles of Na requires 0.205 moles of O2

weight of O2 = no.of moles of O2 * mol.wt of O2 = 0.205*32 = 6.56 gm.

18.9 gm of Na requires 6.56 gm. of O2