Which of the following is not a feature of iron (iii) oxide?
(a) red-orange in colour
(b) forms a protective barrier
(c) falls off in flakes
(d) requires moisture to form

answer: option (a) is the correct answer.

explanation:

the measurement of hydrogen ions in a solution is known as ph.

if ph of a solution is less than 7 then the solution is acidic. if ph of a solution is greater than 7 then the solution is basic.

when the ph of a solution equals 7, then the solution is considered as neutral.

the ph of pure water is 7, therefore, it means that concentration of hydronium ions equals that of hydroxide ions.