Question

Normality of \(0.04 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) is: (a) \(0.02 \mathrm{~N}\) (b) \(0.01 \mathrm{~N}\) (c) \(0.04 \mathrm{~N}\) (d) \(0.08 \mathrm{~N}\)

Short answer

The normality is 0.08 N, so the answer is (d).

Step-by-step solution

Understanding Molarity and Normality

Molarity (M) refers to the concentration of a solution, measured as moles of solute per liter of solution. Normality (N) is a measure of concentration equivalent to molarity but takes into account the number of equivalents per mole of solute. For acids, the number of equivalents often corresponds to the number of hydrogen ions (H) each molecule of acid can release.

Determine Number of Equivalents for H2SO4

Sulfuric acid (\(\mathrm{H}_2\mathrm{SO}_4\)) is a diprotic acid, meaning each molecule can release two hydrogen ions (\(\mathrm{H}^+\)). Therefore, one mole of \(\mathrm{H}_2\mathrm{SO}_4\) is equivalent to two equivalents because it can donate two protons per molecule.

Calculate Normality from Molarity

To calculate normality from molarity, use the formula: \[ Normality = Molarity \times \text{number of equivalents} \]In this case: \[ Normality = 0.04 \text{ M} \times 2 = 0.08 \text{ N} \]

Identify the Correct Answer

The normality of the solution, \(0.04 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\), is calculated as \(0.08 \mathrm{~N}\). Therefore, the correct answer is option (d) \(0.08 \mathrm{~N}\).

Key concepts

Molarity

Molarity is a fundamental concept in chemistry that describes the concentration of a solution. It tells us how many moles of a solute are present in a liter of solution. Imagine molarity as a way to keep track of the amount of substances present in a mixture, which is crucial for calculating reactions accurately.

• A mole is a unit for measuring the amount of substance, akin to how dozen means twelve of something.
• One liter of solution containing one mole of a solute has a molarity of 1 M.
• For example, if you have a 1-liter flask, and you add 1 mole of table salt (sodium chloride), the molarity of that solution is 1 M.

Molarity is essential when mixing or reacting chemical substances because it allows chemists to predict how compounds will interact. When you understand molarity, you'll have a clearer picture of how many molecules you are dealing with for any given reaction.

Equivalent Weight

Equivalent weight is a concept used in situations where we need to consider how substances react rather than how much we have. It's especially useful in acid-base chemistry where we are interested in the 'reactivity' of an acid or base rather than its sheer mass.

• Equivalent weight is defined as the mass of a given substance that will supply or react with one mole of hydrogen ions (F^+) in a chemical reaction.
• For acids, it is calculated based on the number of hydrogen ions the acid can donate. For instance, sulfuric acid (H_{2}SO_{4}) can donate two protons, making its equivalent weight half of its molar mass.
• This means if we have one mole of sulfuric acid at its molecular weight, it is said to have two equivalents due to its ability to dissociate two hydrogen ions.

Understanding equivalent weight helps in calculations involving normality, as it makes it possible to account for the actual reactivity of substances.

Acid-Base Chemistry

Acid-base chemistry forms the core of many chemical processes and reactions, focusing on the properties of acids and bases and their reactions. Understanding how acids behave when dissolved in water and react with bases is fundamental.

• Acids are substances that release hydrogen ions (H^+) when dissolved in water, while bases release hydroxide ions (OH^−).
• When an acid and base react, they typically neutralize each other, forming water and a salt through a neutralization reaction. This is why understanding the normality of solutions, which considers ion reactivity, is crucial.
• The acidity or basicity of a solution is often measured by its pH, which measures the concentration of hydrogen ions in the solution. A lower pH indicates a higher concentration of hydrogen ions (more acidic), whereas a higher pH means fewer hydrogen ions (more basic).

By exploring the rules of acid and base interactions and their calculations, such as those using normality, you will gain insights into many processes around you, from digesting food to manufacturing soap.