I have a solid dissolved in water, both the same temp, and when it's put in the temperature drops. I have the heat capacity it of the solution, and need to the molar heat of the solution of the solid that was dissolved.
Right now I've got:
Mass of water x heat capacity x change in temp.
Then I converted the amount in grams of solid to moles, and divided the heat I got by it.
Am I doing this right? Should I be adding the mass of the solute/solid to the mass of the water? Or just using the mass of the water like I am? I keep finding pages that do it different ways.
It appears tp me ou have done it right. You do not add the mass of the solid to the water. You solved for q and got delta H/mol by dividing by the mols of the solid. The only thing left, I think, is to convert J/mol to kJ/mol since that is the usual way of calculating it but if your problem doesn't actually say kJ/mol you may not need to do it.
Yea, I do have to go to kJ/mol. Just wanted to focus on that step for the question here. Thanks.
You're on the right track! To determine the molar heat of the solution for the solid that was dissolved, you'll need to consider the mass of both the water and the solid.
Here's the step-by-step process:
1. Calculate the heat transferred by the water using the formula:
Heat transferred by water = (Mass of water) x (Heat capacity of the solution) x (Change in temperature)
2. Convert the mass of the solid to moles. To do this, divide the mass of the solid by its molar mass. The result will give you the number of moles of the solid.
3. Divide the heat transferred by water (from Step 1) by the number of moles of the solid (from Step 2). This will give you the molar heat of the solution for the solid that was dissolved.
Regarding your question about including the mass of the solute/solid in the calculation, it depends on whether the mass of the solid is significant compared to the mass of water. If the mass of the solid is relatively small compared to the mass of water, you can neglect it in your calculation. However, if the mass of the solid is significant, it is better to include it in order to obtain a more accurate result.
Keep in mind that the heat capacity you are using should be the heat capacity per unit mass of the solution, not just the heat capacity of water alone.
I hope this helps! Let me know if you have any further questions.