HCl
 

Is it really stomach acid (HCl) has pH 6.0-7.0

Re: HCl
 

Stomach acid (or gastric juice) contains a number of components: the enzymes pepsin and rennin, mucus, and yes, hydrochloric acid. The pH of gastric juice is generally in the range of 1-3.

HCl by itself is a gas, and is called hydrogen chloride. The term hydrochloric acid refers to this gas dissolved in water. Hydrochloric acid can have any number of values for it's pH, depending on how concentrated it is. Highly concentrated HCl(aq) is extremely low pH; I don't know how low it gets exactly. You could calculate it if you cared; the strongest HCl(aq) is 38% by weight HCl.

If you are interested in finding the Ph of a substance use this equation.
-log[H3O]

I write pH = -log₁₀[H⁺] , but the two equations are the same really.

Taking RobJims's 38% by weight HCl means 38g of HCl in 100 ml of solution.

38g of HCl = 1.04 mol in 100 ml of solution = 10.4 M

If [H⁺] = 10.4 M, then pH = -log₁₀[10.4] = -1.0

So the highest possible pH of HCl solution would be -1.0

It's not like that in your stomach though, you wouldn't be in the land of the living. :D

HCl
 

If it is 38% (w/w), then it is 38g HCl in 100 g solution. If it is 38% (w/v), then it is 38 g HCl in 100 mL solution. If it says 38% by weight or by mass, then it is (w/w).:)

I remember a few years back our science teacher told us that if we wanted to know what hydrochloric acid tasted of, vomit was the answer. When we vomit, he told us, we bring up partially digested food and stomach acid. He told us that vomit got its taste from the hydrochloric acid.

I've never tasted HCl, but I've smelt it and it smells nothing like vomit.

I found out later that our science teacher had believed and repeated a myth.