Posted by Ricky on .
At 298.K and 1.00 atm, assume that 22 mL of NO gas reacts with 18 mL of oxygen gas and excess water to produce nitric acid according to the following equation:
2 NO(g) + 3/2 O2 (g)+ H2O(l)?? 2 HNO3(g).
If all of the nitric acid produced by this reaction is collected and then dissolved
into 25 mL of water, what would be the pH of the resulting solution? (Hint: before you begin, think about which reactant is the limiting reagent.)
Use PV = nRT to convert NO to moles. Do the same and find moles ox oxygen.
Using the coefficients in the balanced equation, convert moles NO to moles HNO3.
Same procedure, convert moles O2 to moles HNO3.
It is likely that the two numbers will not agree which means one of them is wrong. The correct value in limiting reagent problems is ALWAYS the smaller one and the reagent producing that value is the limiting reagent.
To find pH, use the smaller value in the previous step, divide by 0.025 L (25 mL) to convert to molarity, then
pH = -log(H^+). The (H^+) will be the molarity of HNO3.
Post your work if you get stuck.