3 Cu + 8HNO3 → 3 Cu(NO3)2 + 2 NO + 4 H2O In the above equation, how many grams of water can be made when 12.6 moles of HNO3 are consumed?

Question

3 Cu  +   8HNO₃ → 3 Cu(NO₃)₂   +  2 NO  +  4  H₂O

In the above equation, how many grams of water can be made when 12.6 moles of HNO₃ are consumed?

 

Round your answer to the nearest tenth. If you answer is a whole number like 4, report the answer as 4.0

Use the following molar masses. If you do not use these masses, the computer will mark your answer incorrect.:

Element	Molar Mass
Hydrogen	1
Nitrogen	14
Copper	63.5
Oxygen	16

Answer 1

Hi Nathan,

We can use the stoichiometric ratio of H₂O to HNO₃ to solve this problem. This is just the ratio of their coefficients in the chemical reaction equation (4 H₂O : 8 HNO₃). In other words, if we scale this ratio to molar quantities, then 4 moles of H₂O are produced for every 8 moles of HNO₃ consumed.

We are given 12.6 moles of HNO₃ and can assume that all of it will be consumed in this reaction. Since we are asked to find the mass of H₂O produced, we can also use the conversion factor of 1 mol H₂O / 18 g (found from the above table by summing the molar mass of each atom in the water molecule).

12.6 mol HNO₃ * (4 mol H₂O / 8 mol HNO₃) * (18 g H₂O / 1 mol H₂O) = 113.4 g H₂O

Notice how the units cancel to give us a final unit of "g H₂O"

You are asked to round to the nearest tenth, so this becomes 113.0 g H₂O