Which terms represents the fixed proportion of elements in a compound

Protons

Explanation:

I'm not exactly sure if this is what your question, but the number of protons is what makes an atom that atom. If you change the number of proton it is now a different atom. You change the number of electrons and get an ion or change the number of neutrons and get an isotope but you can't change the number of protons as you would be changing the elemnt.

what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023 

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.