Thermochemistry

[Pisiform]

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When 9.55g sample of solid NaOH dissolves in 100g of calorimeter in coffee-cup calorimeter, the temperature rises from 23.6 to 47.4 Celsius. Calculate Delta H (in KJ/mole NaOH) for the solution process.

NaOH(s) ----> Na+(aq) + OH-(aq)

Assume that specefic heat of solution is the same as that of pure water.

Answer: -45.7KJ/mole NaOH

Hey guys I really appreciate it if u help me out. I am going through brain fart right now. I appreciate it, I really do.

 

[Salient]

It takes 4.184 Joules to change one gram of water by one degree Celsius.

Since you changed 109.55 grams of water by 23.8 degrees Celsius, you released 10908 Joules, or 10.9 KJ.

this energy was released by 9.55 g of NaOH.

So to recap: 9.55g NaOH releases 10.9 KJ of energy when it dissolves.

9.55g of NaOH at 40 g/mol is 0.238 moles.

So 10.9 KJ/0.238 moles = 45.8 KJ/mol

it's clearly exothermic, so the sign is negative.

 

[Pisiform]

You are awesome 😍

That was really a brain fart 🙂