2 H2 + O2 → 2 H2O
How many grams of H2O are produced when 2.50 moles of oxygen are used?

90g

Explanation:

The equation for the reaction is given below:

2H2 + O2 → 2H2O

From the equation above,

1 mole of O2 produced 2 moles of H2O.

Therefore, 2.5 moles of O2 will produce = 2.5 x 2 = 5 moles of H2O.

Now let us convert 5 moles to H2O to grams to obtain the desired result. This is shown below:

Molar Mass of H2O = (2x1) + 16 = 2 + 16 = 18g/mol

Number of mole of H2O = 5 moles

Mass of H2O = ?

Mass = number of mole x molar Mass

Mass of H2O = 5 x 18 = 90g

Therefore, 90g of H2O are produced

b is the correct