Test: Buffer Solutions - ACT MCQ

Ammonium hydroxide / ammonium chloride is a basic buffer, henderson hasselbalch equation is given by pH = pK_a + log[salt]/[acid] and pH + pOH = 14. So the only correct statement is that boric acid / borax is an acidic buffer.

According to the Henderson hasselbalch equation pH = pK_a + log[salt]/[acid], if we substitute the concentration of salt as 1 M and the concentration of acid as 0.8 M, pH = 4.752 + 0.097 = 4.849 is the required answer.

Buffer capacity is denoted by Φ = number of moles of acid or base added to one litre of the buffer by a change in pH. Here the change in pH is given by 1 and the buffer capacity is given by 2, therefore by substituting, we get that 2 moles of acid or base are added in one litre of the solution.

If the addition of a strong acid or base changes the pH of a buffer by unit, the buffer solution is assumed to be destroyed that is new pH = pK_a ± 1; that means [salt]/[acid] or [acid]/[salt] = 10 or 1/10.

An acidic buffer has a pH value of less than 7, Acetic Acid-Sodium Acetate and boric acid-borax are examples of acidic buffers, but ammonium Hydroxide-ammonium chloride has a pH of greater than 7, so they are basic buffers.

We know that the sum of the pH and pOH of any substance is equal to 14 that is pH + pOH = 14. So here the pH of a substance is given by 3 the pH of the substance = 14 – 3 = 11, 11 is the required answer.

We have henderson-hasselbalch equation as pH = pK_a + log[salt]/[acid]. So by substituting the concentrations of silent and acid along with the acid dissociation constant, we get pH = -log[1.8 × 10^-5] + log [0.50mol/L]/[0.20mol/L] = 5.14.

Buffer capacity is defined as the number of moles of acid or base added in one litre of the solution to change the pH by Unity. Therefore here buffer capacity = 3/5 divided by 2 = 0.6/2 = 0.3. The buffer capacity is given as 0.3.

Equation that is used to calculate the pH of a buffer solution for an acidic buffer is pH = pK_a + log[salt]/[acid]. This equation is known as henderson-hasselbalch equation, it is used for making of buffer solutions.

A solution that resists the change in its PH value by the addition of a small amount of acid or base is called a buffer solution. The buffer system present in the blood is carbonic acid and sodium bicarbonate.