Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

9. Solutions

Equivalents

GOB Chemistry

9. Solutions

Equivalents

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1:48 minutes

Problem 72a

Textbook Question

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

Verified step by step guidance

Understand the concept of equivalents: An equivalent (Eq) is a measure of reactive capacity. For ions, it is calculated based on the charge of the ion. For calcium ion (Ca²⁺), 1 mole of Ca²⁺ provides 2 equivalents because its charge is +2.

Determine the molar mass of calcium (Ca): Look up the atomic mass of calcium on the periodic table. The molar mass of calcium is approximately 40.08 g/mol.

Relate equivalents to moles: Use the relationship between equivalents and moles for Ca²⁺. Since 1 mole of Ca²⁺ equals 2 Eq, the number of moles corresponding to 0.25 Eq can be calculated as: \( \text{moles of Ca}^{2+} = \frac{\text{Eq of Ca}^{2+}}{2} \).

Calculate the mass of calcium: Use the formula \( \text{mass} = \text{moles} \times \text{molar mass} \). Substitute the moles of Ca²⁺ (from the previous step) and the molar mass of calcium to find the mass required.

Combine all the steps: First, calculate the moles of Ca²⁺ from the equivalents, then multiply by the molar mass to find the mass of calcium needed for 0.25 Eq.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equivalent Weight

Equivalent weight is the mass of a substance that will combine with or displace one mole of hydrogen atoms or one mole of electrons in a chemical 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.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is a fundamental property used to convert between the mass of a substance and the number of moles. For calcium ions (Ca²⁺), the molar mass is approximately 40.08 g/mol, 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 allows for the calculation of the amounts of substances involved based on balanced chemical equations. In this context, stoichiometry is used to relate the number of equivalents of calcium ions to the mass needed for a specific reaction or solution.

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Related Practice

Textbook Question

When Michelle's blood was tested, the chloride level was 0.45 g/dL.

b. According to TABLE 9.6, is this value above, below, or within the normal range?

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Textbook Question

A typical oral rehydration solution (ORS) for infants contains 90 mEq/L Na⁺, 20 mEq/L K⁺, 110 mEq/L Cl^– and 2.0% (m/v) glucose (MW = 180g/mol).

b. What is the osmolarity of the solution, and how does it compare with the osmolarity of blood plasma?

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Textbook Question

A typical oral rehydration solution (ORS) for infants contains 90 mEq/L Na⁺, 20 mEq/L K⁺, 110 mEq/L Cl^- , and 2.0% (m/v) glucose (MW = 180g/mol)

a. Calculate the concentration of each ORS component in units of molarity.

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Textbook Question

What does it mean when we say that the concentration of Ca²⁺ in blood is 3.0 mEq/L?

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Textbook Question

The concentration of Cl^- ion in blood is approximately 100 mEq/L. How many milliliters of blood would be needed to obtain 1.0 g of Cl^- ions?

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Textbook Question

Emergency treatment of cardiac arrest victims sometimes involves injection of a calcium chloride solution directly into the heart muscle. How many grams of CaCl₂ are administered in an injection of 5.0 mL of a 5.0% (m/v) solution? How many milliequivalents of Ca²⁺?

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Textbook Question

When Jeff's blood was tested, the chloride level was 0.45 g/dL.

b. According to Table 9.6, is this value above, below, or within the normal range?

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Multiple Choice

Calculate mass (grams) needed for the following ion equivalent:1.5 mEq of Na⁺ ions.