Ahelium balloon contains 0.40 g of helium. given the molecular weight of helium is 4.0 g/mol, how many moles of helium does it contain?

Answer is 0.10 mol.

Explanation;

n = m/M

Where n is number of moles (mol), m is the mass of substance (g) and M is the molar mass of the substance (g/mol).

n = ?

m = 0.40 g

M = 4.0 g/mol

From substitution,

n = 0.40 g /4.0 g/mol

n = 0.10 mol

Hence, the balloon has 0.10 mol of He.

if you mean hydrogen and oxygen then water is the product

because of all the things that happen around the us, many people get into arguments which sadly could get physical, but we should actually make a change for that.