Ch.4 - Chemical Quantities & Aqueous ReactionsWorksheetSee all chapters
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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Hard water contains Ca2+, Mg2+, and Fe2+, which interfere with the action of soap and leave an insoluble coating on the insides of containers and pipes when heated. Water softeners replace these ions

Problem

Hard water contains Ca2+, Mg2+, and Fe2+, which interfere with the action of soap and leave an insoluble coating on the insides of containers and pipes when heated. Water softeners replace these ions with Na+. Keep in mind that charge balance must be maintained.

If 1600. L of hard water contains 0.021 M Ca2+ and 0.0050 M Mg2+, how many moles of Na+ is needed to replace these ions?

Solution

We are asked to determine the number of moles of Na+ needed to replace Ca2+ and Mg2+.


In order for us to solve this problem, we shall follow these steps:

Step 1: Determine the number of moles of each Ca2+ and Mg2+ using the volume of hard water.

Step 2: Perform a mole-to-mole comparison (1 mol Ca2+:2 mol charge and 1 Mg2+:2 mol charge).

Step 3: Get the total mole charge and perform a mole-to-mole comparison with Na+ ion (1 mol charge: 1 mol Na+).


We can use this similar video at Clutch as a guide:

https://www.clutchprep.com/chemistry/practice-problems/69290/hard-water-contains-ca2-mg2-and-fe2-which-interfere-with-the-action-of-soap-and-

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