Answer:
(1) See below, (2) About 8.4 pH, (3) About 3.981 * 10⁻⁶ mol dm⁻³
Explanation:
1. A buffer is a solution that resist pH when adding a basic or acidic compound. It's purpose is to neutralize added acids and bases.
2. Remember that the formula for pH is -log [H+]. We have a 0.1 M solution of baking soda in water with [H+] of about 4.0 × 10⁻⁹. Therefore we can calculate the pH as follows...
pH = -log (4.0 × 10⁻⁹)
pH = -(-8.39794...) = (About) 8.4 pH of 0.1 M of baking soda
3. This question has a similar set up...
pH = -log [H+]
[H+] = inverse of log^- pH
[H+] = 10^-5.4 = (About) 3.981 10⁻⁶