<h3><u>Answer</u>;</h3>
pH = 4.38
<h3><u>Explanation;</u></h3>
Consider that ;
[H3O+] = 10-pH mol/L
Therefore; the pH is the -log of the [hydronium ion].
pH = - log [H3O+]
Thus;
pH = - log (4.2 × 10^–5)
= 4.38
Inquiry; wanting to know. Thinking critically to figure out, understand. However being skeptic to not fall on one simple answer. For possibly, it could be incorrect.
Concentration: 2.5% w/v
Concentration w/v % = [mass of solute / volume of solution ] * 100
=> mass of solute = concentration w/v * volume of solution / 100
=> mass of solute = 2.5 * 750 ml / 100 = 18.75 grams
Also, using proportions you get to the same result:
2.5% w/v => 2.5 grams of NaOH / 100 ml of water
=> 2.5 grams of NaOH / 100 ml water = x grams of NaOH / 750 ml water
=> x grams of NaOH = 750 ml water * 2.5 grams of NaOH / 100 ml water
=> x = 18.75 grams of NaOH
Answer = 18.75 grams of NaOH
