Question

How many equivalents are in \(75.0 \mathrm{~mL}\) of \(0.12 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) solution? In \(75.0 \mathrm{~mL}\) of a \(0.12 \mathrm{M} \mathrm{H}_{3} \mathrm{PO}_{4}\) solution?

Short answer

The equivalents in 75.0 mL of 0.12 M H2SO4 is 0.018 equivalents.

Step-by-step solution

Understand Equivalents

In chemistry, equivalents refer to the amount of substance needed to react with or supply one mole of hydrogen ions (H⁺) for an acid or one mole of hydroxide ions (OH⁻) for a base. This is calculated based on the acid's or base's normality.

Calculate Equivalents for H2SO4

The equivalent factor for sulfuric acid (H2SO4) is 2, as it dissociates to give 2 hydrogen ions (H⁺) per molecule. To find the number of equivalents: use the formula \( ext{equivalents} = ext{molarity} \times ext{volume} \times ext{equivalent factor} \).

Key concepts

Acid-Base Reactions

Acid-base reactions are fundamental chemical processes where an acid reacts with a base to produce water and a salt. In simple terms, acids are substances that release hydrogen ions (H⁺), while bases release hydroxide ions (OH⁻). Therefore, when these two react, they bind to form water ( H₂O). The remaining ions combine to form a salt. For instance, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the end products are water and sodium chloride (NaCl), which is common table salt. Understanding these reactions is essential in calculating the equivalents in a solution, as it involves determining how many hydrogen or hydroxide ions can be released by the acid or base. Each molecule of an acid or base can release a specific number of ions, which determines its 'equivalent factor'. This factor is crucial in computations related to the normality and equivalents of solutions.

Normality in Chemistry

Normality is a measure of the concentration equivalent to the molarity but adjusted for the substance's ability to react in a given chemical reaction. It is particularly useful in situations involving acid-base titrations or reactions where the role of ions is paramount. Think of normality (N) as a way to account for the exact reactive capacity of a solution. Normality is calculated using the formula:\[ \text{Normality (N)} = \text{Molarity (M)} \times \text{Equivalent Factor} \]The equivalent factor is determined by how many ions a molecule of the substance can contribute to the reaction. For example, sulfuric acid (H_2SO_4) has an equivalent factor of 2 because it dissociates to release two hydrogen ions per molecule.

Molarity Calculations

Molarity is the concentration of a solution expressed as the number of moles of solute per liter of solution. It's a way to quantify the exact amount of a substance present in a given volume. When calculating molarity, use the formula:\[ \text{Molarity (M)} = \frac{\text{Moles of Solute}}{\text{Liters of Solution}} \]To find the number of moles, you need to know both the mass of the solute and its molar mass. Knowing the molarity helps in determining how many moles of a substance are present in specific amounts of solution, which is particularly important when calculating equivalents in a solution. For example, if we have a 0.12 M solution of sulfuric acid (H_2SO_4), it means there are 0.12 moles of sulfuric acid in every liter of the solution. This molarity is then used in further calculations such as finding normality or determining the total number of equivalents.