Question

a solution of ammonia has a ph of 11.8. what is the concentration of oh⁻ ions in the solution? useful formulas include h₃o⁺ = 10⁻ᵖᴴ, oh⁻ = 10⁻ᵖᴼᴴ, ph + poh = 14, and h₃o⁺oh⁻ = 10⁻¹⁴
○ 1.58 × 10⁻¹² m
○ 6.31 × 10⁻³ m
○ 2.20 m
○ 158 m

Explanation:

Step1: Calculate pOH from pH

We know that \(pH + pOH = 14\). Given \(pH = 11.8\), we can find \(pOH\) by rearranging the formula: \(pOH=14 - pH\). Substituting the value of \(pH\), we get \(pOH = 14 - 11.8 = 2.2\).

Step2: Calculate \([OH^-]\) from pOH

We use the formula \([OH^-]=10^{-pOH}\). Substituting \(pOH = 2.2\) into the formula, we have \([OH^-]=10^{-2.2}\). Calculating \(10^{-2.2}\), we can rewrite it as \(10^{-2 - 0.2}=10^{-2}\times10^{-0.2}\). We know that \(10^{-0.2}\approx0.631\), so \(10^{-2}\times0.631 = 0.01\times0.631 = 6.31\times10^{-3}\ M\).

Answer:

\(6.31\times10^{-3}\ M\)