Molar change in solution - Problem, tried solving dont understand

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Homework Statement



How many degrees(Celsius) would the temperature rise if 4,0g of NaOH was initially dissolved in 50mL of water.

Homework Equations



Calculate the molar enthalpy change of solution based on this information:

- 4g NaOH(s) gets dissolved in 250mL of water, and the temperature rose from 19,5 to 23.0 Celsius.
- 4.18 J to raise temperature in 1 gram of water 1 Celsius.
- Water density: 1,0g/mL.
- No energy was exchanged with the surroundings before the temperature change was measured.

I solved this and ended up with 36,575 kJ/mol

The Attempt at a Solution



Here is what I`ve tried:

50ml of water = 50 grams
Molar mass of water: 18,016 g/mol

50/18,016= 2,7753 mol

2,7753 mol * 36,575 kJ/mol= 101kJ

101kJ * 1000= 101000 J

101000/4,18 J/g * Celsius=24162

24162/1000=24,16 Celsius ???

19,5+24,16= 43 Celsius??

I dont understand?
The correct answer is from 19,5 to 37.0 Celsius.
 
Last edited:

Answers and Replies

  • #2
Borek
Mentor
28,816
3,321
I solved this and ended up with 36,575 kJ/mol

Moles of what?

Do you mean 36.6 kJ or 36600 kJ?
 

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