Xgm of NaOH required to neutralise 15meq of HCl.To neutralise the same meq of sulphuric acid and phosphoric acid,the weight of NaOH will be.......?

To determine the amount of sodium hydroxide (NaOH) required to neutralize 15 milliequivalents (meq) of hydrochloric acid (HCl), we first need to understand the concept of equivalents and how they relate to the neutralization reactions of different acids.

Understanding Neutralization

Neutralization is a chemical reaction where an acid reacts with a base to produce water and a salt. The number of equivalents is a way to express the reactive capacity of an acid or base. For strong acids like HCl, one equivalent corresponds to one mole of H+ ions. Therefore, 15 meq of HCl means there are 15 millimoles of H+ ions available for reaction.

Calculating NaOH for HCl

Since NaOH is a strong base that dissociates completely in solution, it will react with HCl in a 1:1 ratio. This means that to neutralize 15 meq of HCl, you will also need 15 meq of NaOH. To convert milliequivalents to grams, we can use the formula:

• Weight (g) = (meq × Equivalent weight)

The equivalent weight of NaOH is its molar mass divided by the number of hydroxide ions it can donate, which is 1. The molar mass of NaOH is approximately 40 g/mol. Therefore, the equivalent weight is also 40 g/equiv.

Now, substituting the values:

• Weight of NaOH = 15 meq × (40 g/equiv / 1000 meq/equiv) = 0.6 g

Neutralizing Other Acids

Next, let’s consider the amounts of NaOH needed to neutralize sulfuric acid (H2SO4) and phosphoric acid (H3PO4). The neutralization ratios differ due to the number of acidic protons each acid can donate.

Sulfuric Acid (H2SO4)

Sulfuric acid is a diprotic acid, meaning it can donate two protons (H+ ions). Therefore, 15 meq of H2SO4 corresponds to 7.5 meq of NaOH because:

• 15 meq H2SO4 × (1 equiv H2SO4 / 2 equiv H+) = 7.5 meq NaOH

Now, calculating the weight of NaOH needed:

• Weight of NaOH = 7.5 meq × (40 g/equiv / 1000 meq/equiv) = 0.3 g

Phosphoric Acid (H3PO4)

Phosphoric acid is a triprotic acid, meaning it can donate three protons. Thus, 15 meq of H3PO4 corresponds to 5 meq of NaOH:

• 15 meq H3PO4 × (1 equiv H3PO4 / 3 equiv H+) = 5 meq NaOH

Calculating the weight of NaOH for phosphoric acid:

• Weight of NaOH = 5 meq × (40 g/equiv / 1000 meq/equiv) = 0.2 g

Summary of Results

To summarize, the amounts of NaOH required to neutralize 15 meq of each acid are:

• For HCl: 0.6 g of NaOH
• For H2SO4: 0.3 g of NaOH
• For H3PO4: 0.2 g of NaOH

This illustrates how the number of acidic protons in different acids affects the amount of base needed for neutralization. Understanding these relationships is crucial in chemistry, especially in titration and acid-base reaction contexts.