Question

Record the mass of the beaker and its contents.

Data

Calculations

The reaction that occurred is:
NaHCO3 (s) + HCl (aq)  NaCl (aq) + H2O (l) + CO2 (g)

ΔH = +28 kJ/mol

Mass of beaker	Mass of baking soda	Volume and molarity of acid	Lowest Temperature	Mass of beaker and contents
100.7g	3.150g	250ml and 2M	13.44 Celsius	114.55g

1. Calculate the number of kJ absorbed by the reaction assuming the baking soda was the limiting reactant.

2. Convert the kJ into calories.

3. Divide the calories by the number of grams of solution you have in your beaker.

   This will give you a theoretical value for how much your temperature should have

   dropped during the reaction.

4. Compare your theoretical temperature drop from with the experimental

5. . Calculate the moles of HCl present in the experiment. Was it correct to assume that the baking soda was the limiting reactant?

Answer 1

First we need to calculate the number of moles of limiting reactant, which is sodium bicarbonate. We can do this using:

We know the reaction absorbs 28 kJ per mole, so 0.0375 moles absorb:

Which is (in cal:)

We have a total mass of:

So the calories per gram are:

I don't know which was the drop in temperature of your experiment, so I can't help you with the comparison!

The number of moles of HCl is given by:

Which is higher than the number of moles of sodium bicarbonate, so the choice of limiting reactant was correct.