Question

(a) What effect does the concentration of $H^{+}$ (aq) ions have on the nature of a solution?

(b) What effect does the concentration of $O{H}^{-}$ ions have on the nature of a solution?

(c) Someone put some universal indicator paper into vinegar. The pH is 3. What does this tell you about the vinegar?

(d) Someone put some universal indicator paper onto wet soap. the pH is 8. What does this tell you about the soap?

(e) State whether a solution is acidic. alkaline or neutral if its pH is :

(i) 9

(ii) 4

(iii) 7

(iv) 1

(v) 10

(vi) 3

Answer 1

(a)If the concentration of $H^{+}$ (aq) ions is increased($>{10}^{-7}$ ) then the solution becomes acidic and if the concentration of $H^{+}$ (aq) ions is decreased($<{10}^{-7}$ ) then the solution becomes basic in nature.
The concentration of $H^{+}$ (aq) ions determines the acidic nature of a solution. Hence, the acidity of a solution increases with increases in the concentration of $H^{+}$(aq) ions and vice versa.

(b)As the concentration of hydroxide ions increases the solution becomes more basic. Hydroxide ions are molecular ions with the formula $O{H}^{-}$, formed by the loss of a proton from a water molecule. The hydration of the hydroxide ion ($O{H}^{-}$ ) is very important for biological and non-biological processes.
When an acid is dissolved in water, the balance between hydrogen ions and hydroxide ions is shifted. Now there are more hydrogen ions than hydroxide ions in the solution. This kind of solution is acidic.

(c)Vinegar is acidic in nature.

(d) Soap is basic in nature.

(e)

(i) pH =9 :Alkaline

(ii) pH =4 : Acidic

(iii) pH = 7 : Neutral

(iv) pH =1 : Acidic

(v) pH =10 : Alkaline

(vi)pH= 3 : Acidic