which substance functions to control the release of hydrochloric acid to prevent excessive acidity?

Solution:

A compound consisting of hydrogen and chlorine. Hydrochloric acid is secreted in the stomach and is a major component of gastric juice. A clear, colorless, fuming, poisonous, highly acidic aqueous solution of hydrogen chloride, HCl,it is a chemical intermediate used in, food processing, pickling, and metal cleaning. It is found in the stomach in dilute form. HCI is Hydrogen (H), Carbon (C) and Iodine (I). Although,  

HCI is not balanced, so, that would actually be an ion, with negative charge.a hormone that stimulates secretion of gastric juice, and is secreted into the bloodstream by the stomach wall in response to the presence of food.

thus for controlling  Gastrin is used.

Gastrin is a peptide hormone that stimulates secretion of gastric juice (HCl) by the partial cell of the stomach and aids in gastric motility. It is released by G cells in the pyloric antrum of the stomach.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol