Reaction of sodium carbonate in ethanoic acid. This is an example of an endothermic (heat absorbing) acid-carbonate reaction, which produces a metal salt. Ethanoic, or acetic, acid is a weak acid found in vinegar (here 6% wine vinegar). Here the sodium carbonate has not yet been added and the starting temperature is 16 degrees Celsius. This reaction produces sodium ethanoate (sodium acetate) and a temperature drop of 6.4 degrees, to 9.6 degrees Celsius (see image: C008/4187).