[leah106]

This is my last question today, I promise!

The very last question on my lab report asks, "If you used 1.0 M HCl by mistake, would it change your results? Explain and show your calculations."

For this part of the lab I combined Magnesium Oxide with 3M HCl in a calorimeter and found the change in temperature. Then using my starting amounts, 75.0mL of 3.0 M HCl and 2.050 g MnO, I calculated the mass of HCl, Total Mass, Moles of HCl, Mols of MgO, and Standard Enthalpy of Formation of MgO.

Where would molarity of HCl come in to play in my calculations, if at all?

Earlier I asked about using Molarity of HCl to calculate the mols of HCl used, however my lab notebook said to use the density of a dilute aqueous solution (1.01g/mL) to do that instead. So instead of using molarity, I went with the second way. That's the only place in my calculations I remember taking the molarity of HCl into consideration, and even then I didn't use it in my calculations. So I want to say using 1 M HCl instead of 3 M HCl wouldn't affect anything, however I know that can't be right. Where did I mess up and forget to include Molarity in my calculations?

[fledarmus]

I'm not sure now whether you're working with Mn or Mg, but as a start, how would the density of the HCl solution change? What about the moles of HCl present in the reaction? Does this change the final number of moles of product?