Calculate the mass needed for each of the following ion equivalents: 0.25 Eq Ca²⁺

Verified step by step guidance

1. Identify the charge of the ion. Calcium (Ca) has a charge of +2, which means it is a divalent ion.
2. Understand the concept of equivalents. One equivalent (Eq) of an ion is the amount that supplies or consumes one mole of charge. For Ca²⁺, 1 Eq corresponds to 0.5 moles of Ca²⁺ because it has a charge of +2.
3. Calculate the number of moles of Ca²⁺ needed for 0.25 Eq. Since 1 Eq is 0.5 moles, 0.25 Eq will be 0.25 * 0.5 moles.
4. Determine the molar mass of calcium (Ca). The atomic mass of calcium is approximately 40.08 g/mol.
5. Calculate the mass of calcium needed by multiplying the number of moles by the molar mass of calcium.

Key Concepts

Equivalent Weight

Equivalent weight is the mass of a substance that can combine with or displace one mole of hydrogen ions (H⁺) in a reaction. For ions, it is calculated by dividing the molar mass of the ion by its charge. Understanding equivalent weight is crucial for determining how much of a substance is needed to achieve a specific ionic concentration in a solution.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For calcium ions (Ca²⁺), the molar mass is approximately 40.08 g/mol. Knowing the molar mass allows for the conversion between moles and grams, which is essential for calculating the mass required for a given number of equivalents.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It involves using balanced chemical equations to calculate the amounts of substances involved. In this context, stoichiometry helps in determining how much mass of Ca²⁺ is needed to provide 0.25 equivalents based on its molar mass and charge.