# Closed container vs Open container for calorimetry

1. Nov 10, 2017

### Matthew Hoffman

So let's say I do the reaction Mg + HCl --> MgCl2 + H2 in an open calorimeter. I measure a certain temperature change in the calorimeter, let's say an increase of 12 degrees C. Keeping all other variables the same, if I perform this experiment in a closed calorimeter, what will happen to the measured temperature? I know the pressure of the gas will increase because of the compressed H2, but will this have any affect on the temperature of the liquid below it?

2. Nov 14, 2017 at 10:38 PM

### Bystander

Does the H2 have a non-zero heat capacity?

3. Nov 16, 2017 at 11:23 PM

### Matthew Hoffman

H2 does have a nonzero heat capacity. At 300K, it is 14.31 (kJ/(kg K)). Compared to air, which has a value of 1.00. And in a closed container, the mixture of gases would contain much more H2 than in an open container where it would escape. Am I headed in the right direction here?

4. Nov 16, 2017 at 11:29 PM

### Bystander

... and?

5. Nov 16, 2017 at 11:31 PM

### Matthew Hoffman

And... since H2 has a greater heat capacity its temperature will not increase as much as plain air, so that means the measured temperature in the calorimeter would be less?

6. Nov 16, 2017 at 11:37 PM

### Bystander

Period, no need to compare it to air. Do you have any air reacting?

7. Nov 16, 2017 at 11:43 PM

### Matthew Hoffman

No, the reaction is only taking place in the liquid