These are two questions and two answers:
1) Which of the following is not a property of an acid?
A. Turns litmus paper blue
B. Corrodes active metals
C. Turns litmus paper red
D. Neutralize bases
Answer: option A) turns litmus paper blue.
Explanation:
Indicators are compounds used to show the approximate acidity of a substace by showing a specific color depending on the pH.
Litmus paper is one of those indicators. It turns red when the pH is 4.5 and turns blue when the pH is above 8.2.
The pH of acids is below 7 (above 7 the substance is not an acid but a base).
Then, acids turns the litmus paper red, not blue.
2) Acid compounds contain ____.
A. Molecules
B. Ions
C. Oxygen
D. Hydrogen
Answers: option B. ions
Explanation:
Keep in mind these definitions of acids as per the different theories:
Arrhenius (the oldest definition): acids are substances that contains hydrogens and inoizes producing H⁺.
Bronsted-Lowry: acids are substances that donates hydrogen ions, H⁺ (coincides with Arrhenius definition)
Lewis (the most general definition): an acid is an acceptor of electron-pais.
I would like to start with the easy part of discarding options C and D.
C. All the acid compounds contain oxygen?
No. The binary acids, like HF, HCl, HBr, H₂S to not containd oxygen.
D. All acids contains hydrogens?
No. Arrhenius and Bronsted-Lowry theories do define acids in terms of hydrogens and you might say that most acids have hydrogens. But as per Lewis acids bases theory acids are substances that accept eletron-pairs. So, this definition does not need that a substance has hydrogens to be an acid. Some examples of Lewis acids that do not have hydrogens are BF₃ and AlB₃, among others.
Now go with the other options.
A) Acid compounds contains molecules?
Stron acids are fully dissociated which means that they exist as ions not molecules.
That leaves only the option B. ions.
Indeed as per any definition Arrhenius, Bronsted-Lowry or Lewis, acids contains ions. Under Lewis definition, the most generic ot them, an acid is a substance that accepts elctron-pairs. That is becasue the positve ion of the substance can deal with those electron-pairs.
