# Homework Help: Hydrochloric Acid & Marble Chips (CaCO3)

1. Dec 22, 2005

### GumzyG

Hello. I am looking for some results of the experiment. The results should be the loss in weight of the marble chips with the Acid at different strengths ( 2M, 1M, 0.5M, 0.25M and 0.25M).

Thanks.

2. Dec 22, 2005

### mrjeffy321

The loss in wieight would be the Carbon Dioxide that escapes.

CaCO3 + 2 HCl --> CaCl2 + H2CO3
H2CO3 --> H2O + CO2

Assuming the reaction is completed, it shouldnt matter too much what the concentration of the acid is as long as the Carbonic acid (H2CO3) decomposes.

The experiment shouldnt be that hard to preform, just weight out all the reactants ahead of time, and measure the weight at the end. The difference should be the weight of the CO2. From this, you could back calculate exactly how much H2CO3 was formed and then how much CaCO3 reactanted.

3. Jan 1, 2006

### GumzyG

Does this reaction give off heat?

4. Jan 6, 2006

### Mattara

It is near impossible to tell that from just studying the reaction if the particular reaction is exotermic (heat is given out) or endotermic (heat is absorbed).

I would recommend some sort of enthalpy diagram

First reaction:

bonds broken:

1*[Ca-C]
3*[C-O]
2*[H-Cl]

bonds form:

2*[Ca-Cl]
3*[C-O]
2*[O-H]

Second reaction:

Bonds broken:

3*[C-O]
2*[O-H]

Bonds formed:

2*[C=O]
2*[O-H]

I'm not near a bond enthalpy table so i can't do the entire math right now.

Do this for both reactions:

enthalpy for the products - enthalpy for the reactants = ?

Is this answer negative, then energy has been given out, if it is positive, energy has been absorbed (it is from the view of the substance).