Question

I'm having trouble with Calorimetry.

Answer 1

Alright so my data was already a given:

Data and Observations:

Volume of H2O
205.0 mL H2O
Mass of NaOH
2.535 g NaOH
Initial temperature in calorimeter
24.2 °C
Final temperature in calorimeter
27.8 °C

Answer 2

I need help with a few of the questions below. My teacher had given me a few things I needed improvement on.

Calculations:
Show your work and write a short explanation with each calculation.
Write out a balanced "equation" for the process you investigated in Part I, including phase symbols.
NaOH(s) + H2O(l) --> NaOH(aq)

Problem with this was: #1 Balanced reaction include phase and ions

Answer 3

(this is just to fill in information)
Calculate the number of moles of sodium hydroxide dissolved. Show your work.
Moles NaOH = 2.535 grams NaOH * (1 mole/40.00 grams) = 0.06338 moles NaOH

Answer 4

Calculate the amount of energy involved in this dissolving process. Show your work. q = m c (T2-T1)
200 mL H2O * 1 g/1 mL = 200 g H2O
c = 4.184 J/gC
T2 = 27.8 C
T1 = 24.2 C
Heat gained by H2O = 200 g * 4.18 J/gC * (27.8 - 24.2) = 3010 J

I was told: #3 Find moles NaOH by coverting NaOH mL to Liters then use Molarity NaOH to convert to mol NaOH

Answer 5

Determine the enthalpy change, per mole of sodium hydroxide dissolved. Show your work.
3010 J / 0.06338 mol NaOH = 4.75X10^4 J/mole X 1 kJ/1000 J = 47.5 kJ/mol NaOH

I was told: #4 Divide enthalpy change from 2 by moles from 3 to calculate total enthalpy change.

Answer 6

NaOH(s) + H2O(l) --> Na+ + OH-
This formula would give you your ions and they would be aqueous

Answer 7

You would have to balance it still though

Answer 8

I'm not 100% sure on what the I was told #3 part is going for but I'm assuming that it's trying to say that after finding the moles of NaOH you can use that as the number of moles for water and convert it into mass from there but you have to keep in mind stoichimometric coefficients

Answer 9

Don't know about that last part though

Answer 10

Thank you for responding to this o.e

I just kinda posted everything at first to introduce the harder questions to follow anyway. I was hoping to sort of hook someone into reading the easier parts.

Answer 11

Part 2: Data and Observations:

Volume of HCl solution
100.5 mL HCl
Volume of NaOH solution
100.0 mL NaOH
Initial temperature in calorimeter
25.2 °C
Final temperature in calorimeter
28.2 °C

Answer 12

Part 2

Calculations:
#1 Write out a balanced equation for the reaction you investigated in Part II, including phase symbols.
HCl + NaOH -> NaCl + H2O

#2 Determine the enthalpy change of this reaction. The mass of the sodium hydroxide and the mass of the hydrochloric acid should be added together.
q = m × c × Δt
200.5 g of solution
200.5 g * 4.18*(28.2-25.2)= 2514.27 J
-2514.27/1000 = -2.514 kJ
= 1.258 kj/mol
#3 Determine the number of moles of NaOH.

#4 Determine enthalpy per mole of NaOH. Show all of your work.


I was told:
#1 Balanced reaction include phase and ions
#3 Find moles NaOH by coverting NaOH mL to Liters then use Molarity NaOH to convert to mol NaOH
The molarity of NaOH is given in the directions.
#4 Divide enthalpy change from 2 by moles from 3 to calculate total enthalpy change.

Answer 13

Ok I see, I can help you with understanding any of this or helping you calculate. It looks like you worked out everything previously correctly, I was quite thorough but got distracted part way through.

After seeing these problems you were assigned, I guess my question is... What question do you have? Let's just start with one thing at a time because there's a lot here and it's easy to get lost in all this.

Answer 14

I'm sorry that it's a lot, it's sectioned into parts and I'd just like for people to know what they're getting into with helping me.
I guess what I need is a bit of proof calculating? I need the errors pointed out and sort of guided as well.

Answer 15

It's fine don't apologize, I actually appreciate that you've put this much effort into trying to learn so I'm more than happy to help.

So is what you've put currently here new calculations you've done, or are these the old calculations you were told were incorrectly done? I guess, can you go ahead and maybe copy one particular piece from up above and then just ask specifically about that one part what you want me to help with?

Answer 16

They're the old calculations. As a whole assignment, I figured I get help with the easier small questions before I do anything (to get it this time around) to help with Part 3.

Answer 17

alright so I guess I'll just use question 4 from part one.

Determine the enthalpy change, per mole of sodium hydroxide dissolved. Show your work.
3010 J / 0.06338 moles NaOH = 4.75*10^4 J/mole * 1 kJ/1000 J = 47.5

what I was actually told was: "#3 (I guess she forget #3('s) for belonging to it) q surroundings = -q system Use -q for #4 Enthalpy Change." so I kinda need help with just seeing that itself. Once I've already done something, I usually just continue to see it that way.

Answer 18

Ahhh ok I think I see what you mean. So enthalpy is the heat, and heat is energy. Since energy is conserved that means whatever heat you put into something had to come out of something.

In this case, we heated up the water, we could tell because the temperature of the water rose. However the NaOH molecules originally had this energy in them, it was transferred out, and this was actually lost. So while what you calculated was q for the water, what you wanted was the q for the reaction itself which was -q since it lost heat in order to heat up the water.

Does that answer that question for why the sign has to be negative for exothermic reactions? (reactions where heat is lost and put into the solution)

Answer 19

wait, I basically missed this because of a negative sign? xD

Answer 20

Yeah it sounds like it hah

Answer 21

Hey, I still haven't submitted this assignment, could you help draw out these questions and help me before I have to submit it? I've been in and out of doing school work ._.