Question

the ph reading of a sample of each substance is given. calculate the hydrogen ion concentration of the substance. (give your answers in scientific notation, correct to one decimal place.) (a) soda: ph = 2.8 h⁺ = × 10 m (b) milk: ph = 6.7 h⁺ = × 10 m

Explanation:

Step1: Recall the pH formula

The formula for pH is $pH = -\log[H^{+}]$, which can be rewritten as $[H^{+}]=10^{-pH}$.

Step2: Calculate hydrogen - ion concentration for soda

Given $pH = 2.8$ for soda. Substitute into the formula: $[H^{+}]=10^{-2.8}$.
$10^{-2.8}=10^{0.2}\times10^{-3}$. Since $10^{0.2}\approx1.6$, then $[H^{+}]=1.6\times 10^{-3}\text{ M}$.

Step3: Calculate hydrogen - ion concentration for milk

Given $pH = 6.7$ for milk. Substitute into the formula: $[H^{+}]=10^{-6.7}$.
$10^{-6.7}=10^{0.3}\times10^{-7}$. Since $10^{0.3}\approx2.0$, then $[H^{+}]=2.0\times 10^{-7}\text{ M}$.

Answer:

(a) $1.6\times 10^{-3}$
(b) $2.0\times 10^{-7}$