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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 102a

Citric acid, C6H8O7, is a triprotic acid. It occurs naturally in citrus fruits like lemons and has applications in food flavouring and preservatives. A solution containing an unknown concentration of the acid is titrated with KOH. It requires 23.20 mL of 0.500 M KOH solution to titrate all three acidic protons in 100.00 mL of the citric acid solution. Write a balanced net ionic equation for the neutralization reaction.

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Key Concepts

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

Triprotic Acids

Triprotic acids, like citric acid, can donate three protons (H+) per molecule during a reaction. This characteristic affects their behavior in titrations, as each proton can react with a base, leading to multiple equivalence points. Understanding the nature of triprotic acids is essential for determining the stoichiometry of the neutralization reaction.
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Neutralization Reaction

A neutralization reaction occurs when an acid reacts with a base to form water and a salt. In this case, citric acid reacts with potassium hydroxide (KOH) to neutralize its acidic protons. The balanced net ionic equation represents the essential species involved in the reaction, excluding spectator ions, and is crucial for understanding the overall chemical process.
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Titration and Molarity

Titration is a quantitative analytical method used to determine the concentration of an unknown solution by reacting it with a solution of known concentration. Molarity, defined as moles of solute per liter of solution, is key in calculating the amount of acid neutralized by the base. In this scenario, the volume and molarity of KOH allow for the determination of the moles of citric acid present in the solution.
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Related Practice
Textbook Question

Neurotransmitters are molecules that are released by nerve cells to other cells in our bodies, and are needed for muscle motion, thinking, feeling, and memory. Dopamine is a common neurotransmitter in the human brain. (c) Experiments with rats show that if rats are dosed with 3.0 mg/kg of cocaine (that is, 3.0 mg cocaine per kg of animal mass), the concentration of dopamine in their brains increases by 0.75 mM after 60 seconds. Calculate how many molecules of dopamine would be produced in a rat (average brain volume 5.00 mm3) after 60 seconds of a 3.0 mg/kg dose of cocaine.

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Textbook Question

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. (a) If 1500 L of hard water contains 0.020 M Ca2+ and 0.0040 M Mg2+, how many moles of Na+ are needed to replace these ions?

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Textbook Question

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. (b) If the sodium is added to the water softener in the form of NaCl, how many grams of sodium chloride are needed?

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Textbook Question

Citric acid, C6H8O7, is a triprotic acid. It occurs naturally in citrus fruits like lemons and has applications in food flavouring and preservatives. A solution containing an unknown concentration of the acid is titrated with KOH. It requires 23.20 mL of 0.500 M KOH solution to titrate all three acidic protons in 100.00 mL of the citric acid solution. Calculate the molarity of the citric acid solution.

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Textbook Question
(c) If 18.65 mL of the caesium hydroxide solution was needed to neutralize a 42.3 mL aliquot of the hydroiodic acid solution, what is the concentration (molarity) of the acid?
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Textbook Question

Suppose you have 3.00 g of powdered zinc metal, 3.00g of powdered silver metal and 500.0 mL of a 0.2 M copper(II) nitrate solution. (a) Which metal will react with the copper(II) nitrate solution?

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