How many moles of H2O will be produced from 273grams of H2?

136.5moles of H2O

Explanation:

First, let us write a balanced equation for the reaction of Hydrogen to produce water. This is illustrated below:

2H2 + O2 —> 2H2O

Molar Mass of H2 = 2x1 = 2g/mol

Mass of H2 from the question = 273g

Number of mole = Mass /Molar Mass

Number of mole of H2 = 273/2 = 136.5moles

From the equation,

2moles of H2 produced 2moles of H2O.

Therefore, 136.5moles of H2 will also produce 136.5moles of H2O.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.