Molar change in solution - Problem, tried solving dont understand

  • Thread starter Thread starter Gold
  • Start date Start date
  • Tags Tags
    Change
Click For Summary
SUMMARY

The discussion centers on calculating the temperature rise when 4.0g of NaOH is dissolved in 50mL of water. The user initially calculated the molar enthalpy change of solution as 36.575 kJ/mol, leading to an incorrect temperature rise estimate of 43°C. The correct temperature increase should result in a final temperature of 37.0°C from an initial 19.5°C. The confusion arises from the interpretation of the enthalpy value and the moles of water involved in the calculation.

PREREQUISITES
  • Understanding of molar enthalpy change calculations
  • Basic knowledge of thermodynamics and calorimetry
  • Familiarity with the concept of moles and molar mass
  • Ability to perform unit conversions in thermodynamic equations
NEXT STEPS
  • Learn how to accurately calculate molar enthalpy changes using calorimetry
  • Study the principles of thermodynamics related to solution chemistry
  • Explore the concept of specific heat capacity and its applications
  • Investigate common pitfalls in stoichiometric calculations involving solutions
USEFUL FOR

Chemistry students, educators, and anyone involved in thermodynamic calculations related to solutions will benefit from this discussion.

Gold
Messages
1
Reaction score
0

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 don't understand?
The correct answer is from 19,5 to 37.0 Celsius.
 
Last edited:
Physics news on Phys.org
Gold said:
I solved this and ended up with 36,575 kJ/mol

Moles of what?

Do you mean 36.6 kJ or 36600 kJ?
 

Similar threads

Chemistry Thermodynamics: The molar enthelpy of a solution
  • · Replies 2 ·
Replies
2
Views
2K
Calorimetry Problem: Calculate Change in Enthalpy
  • · Replies 16 ·
Replies
16
Views
3K
Does sodium bicarbonate solution release CO2 when heated?
  • · Replies 2 ·
Replies
2
Views
4K
Answer: Evaporative Cooling: Body Temp Drops 0.05°C w/ 10g Water
  • · Replies 1 ·
Replies
1
Views
3K
What Is the Molar Enthalpy of Neutralization of NaOH?
  • · Replies 1 ·
Replies
1
Views
15K
What Is the Final Temperature of a Squeezed Hot Pack with LiCl and Water?
  • · Replies 7 ·
Replies
7
Views
3K
Two questions on colligative properties.
  • · Replies 1 ·
Replies
1
Views
2K
What is the Molar Heat of Neutralization for Sodium Hydroxide?
  • · Replies 1 ·
Replies
1
Views
3K
How Do You Calculate Heat and Enthalpy in an Ice Melting Lab?
  • · Replies 1 ·
Replies
1
Views
5K
Is the traditional method for calculating molar heat of dissolution accurate?
  • · Replies 5 ·
Replies
5
Views
3K