## Lecture example

$\Delta U=q+w$

Shanzey
Posts: 120
Joined: Wed Sep 18, 2019 12:20 am

### Lecture example

In lecture during Monday of week 4, Dr. Lavelle did an example of a neutralization reaction. When he did the question, he used the Q= mC(delta)T equation, which I understand; however, he used 100g as his mass for the equation. In order to find the mass, did he add the 50ml of each solution and then convert to g using the density information given? Do the concentrations of each solution not matter when calculating the heat?

For reference:
e.g. In a constant pressure calorimeter at 25 degrees C mix 50.0 ml each of 1.0M HCL and 1.0M NaOH after mixing T= 31.9 degrees Celsius. Therefore, the neutralization reaction is exothermic. How much heat is released? Assume density of solution is about 1.0 g.ml-1 (pure water and use specific heat capacity of water, 4.18 J.C-1.g-1.
H+ (aq) + OH- (aq) --> H2O (l)

Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

### Re: Lecture example

He used the density of the liquid to find the mass. He did this because specific heat capacity has grams in the units, so it can be interpreted as the amount of energy needed to raise the temperature of one gram of a substance one degree. If he used molar heat capacity, then he would need to find the moles of the substance, and so on.It depends on what the units call for in the given information.

Vinita Saxena 2I
Posts: 58
Joined: Fri Aug 09, 2019 12:16 am

### Re: Lecture example

In this case, specific heat capacity uses grams, but if he had used the molar heat capacity then he would have needed to convert to moles using the concentrations.