Question

which of the following formulas is incorrect?

aioh3

(nh4)2s

naoh

ai2(so4)3

Explanation:

Step1: Analyze the charge of ions

Aluminum ion (\(Al^{3 +}\)) has a charge of \(+ 3\), hydroxide ion (\(OH^{-}\)) has a charge of \(-1\).

Step2: Determine the correct formula of aluminum hydroxide

Using the criss - cross method (the magnitude of the charge of one ion becomes the subscript of the other ion), the formula for aluminum hydroxide should be \(Al(OH)_{3}\) (not \(AlOH_{3}\)).

Step3: Analyze \((NH_{4})_{2}S\)

Ammonium ion (\(NH_{4}^{+}\)) has a charge of \(+1\), sulfide ion (\(S^{2 -}\)) has a charge of \(-2\). Using the criss - cross method, the formula \((NH_{4})_{2}S\) is correct.

Step4: Analyze \(NaOH\)

Sodium ion (\(Na^{+}\)) has a charge of \(+1\), hydroxide ion (\(OH^{-}\)) has a charge of \(-1\). The formula \(NaOH\) is correct.

Step5: Analyze \(Al_{2}(SO_{4})_{3}\)

Aluminum ion (\(Al^{3+}\)) has a charge of \(+3\), sulfate ion (\(SO_{4}^{2 -}\)) has a charge of \(-2\). Using the criss - cross method (\(Al^{3+}\) and \(SO_{4}^{2 -}\), \(2\) and \(3\) as subscripts for \(Al\) and \(SO_{4}\) respectively), the formula \(Al_{2}(SO_{4})_{3}\) is correct.

Answer:

\(AlOH_{3}\)