CHEM120 Lecture 10: CHEM 120 Lecture 10: Types of Acid:Base Reactions

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raspberrymacaw339

29 Nov 2016

School

University of Waterloo

Department

Chemistry

Course

CHEM120

Professor

Richard Marta

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Document Summary

In class we focused on writing net ionic equations for precipitation reactions. Another group of reactions that you are responsible for determining the net ionic equations for are acid-base neutralizations. Acid-base neutralizations involve the transfer of a proton(s) from an acidic species to a basic species. There are four possible scenarios that you can encounter: a strong acid reacting with a strong base, a strong acid with a weak base, a strong base with a weak acid, a weak acid with weak base. Such reactions will normally involve aqueous (aq) species. Memorize the strong acids and bases on page 10 of module 2 in the course notes. Aqueous strong acids and bases will dissociate fully (100%) into their constituent ions. Aqueous weak acids and bases will not dissociate or react fully into ions and will be left intact in the net ionic equation.

Related Questions

Consider the following acid-neutralization reactions involving the strong base NaOH(aq):
HNO₃(aq) + NaOH(aq) NaNO₃(aq) + H₂O(l)
HCl(aq) + NaOH(aq) NaCl(aq) + H₂O(l)
NH₄⁺(aq) + NaOH(aq) NH₃(aq) + Na⁺(aq) + H₂O(l)

(a) By using data in Appendix C, calculate ∆H° for each of the reactions. (b) As we saw in Section 4.3, nitric acid and hydrochloric acid are strong acids. Write net ionic equations for the neutralization of these acids. (c) Compare the values of ∆H° for the first two reactions. What can you conclude? (d) In the third equation NH₄⁺ (aq) is acting as an acid. Based on the value of ∆H° for this reaction, do you think it is a strong or a weak acid? Explain.

orangejackal358

Part A A fuel cell differs from a battery because the current is being generated from a reduction-oxidation (redox) reaction in which the reactant is consumed. A classic example of a fuel cell is the phosphoric acid fuel cell (PAFC), which have been used in stationary power generators, buses, and even submarines. Fuel cells require an electrolyte (similar to batteries) to carry electrically charged species between the electrodes, and a PAFC utilizes phosphoric acid (H3PO4) as its electrolyte. Phosphoric acid has three acidic protons that can dissociate in water, as highlighted in red here: H3PO4. However, it is considered a weak acid because some of the acid will remain in molecular form when dissolved in water. Write the complete ionic equation that depicts the dissociation of the first proton for the weak acid phosphoric acid (H3PO4). Make certain you include all charges for any ions produced. Express you answer as a chemical equation including phases. Titrations as analytical neutralization reactions Neutralization reactions can occur between any combination of weak/strong acids and bases. When we want to determine the concentration of a base in solution, we can apply the concept of neutralization by reacting the base with a known amount of an acid in the presence of an indicator (a compound that changes color depending on the pH). This method of determining the concentration of a base is called acid-base titration, and it can also be used to determine the concentration of an acid by titrating it with a known amount of base. A common acid to use for titrations is potassium hydrogen phthalate (written as KHP or KHPh; do not confuse the P for phosphorus). The reason KHP is common is because it is solid at room temperature, and we can accurately mass the amount that is added to solution. As a soluble salt, KHP completely dissociates to form a potassium ion (K+) and an acidic hydrogen phthalate ion (HPâ), which is a weak acid that has only one acidic hydrogen. This ionization is depicted below. KHP(s) â K+(aq)+HPâ(aq) Although ionization (the formation of ions) occurs as a result of acid dissociation for most weak acids, KHP ionizes before acid dissociation occurs. In other words, HPâ is a weak acid ion. Part C If you wanted to determine how much KOH (potassium hydroxide; a strong base) was dissolved in water, you could titrate it with a known amount of KHP (potassium hydrogen phthalate; a weak acid) until a color change indicates that the base is completely neutralized. The molecular equation below depicts this neutralization reaction. KHP(aq)+KOH(aq)âK2P(aq)+H2O(l) Write the net ionic equation that depicts the neutralization of the base by potassium hydrogen phthalate. Instead of using the entire chemical formula of phthalate, use HPâ to represent the acidic hydrogen phthalate ion and P2â to represent the phthalate ion. Express your answer as a net ionic equation including phases.

Why do ionic compounds dissolve well in water? Select all that are true.

Question 5 options:

Because water and ionic compounds are both polar

Water molecules have partial charges that attract the ions in the solid compound, causing it to dissociate into separated ions

Because organic compounds are nonpolar

Water molecules can surround an ion, and neutralize the ion's charge using either it's partial positive or negative side.

The individual ions are solvated by water molecules which stabilizes the ions

2. Which compound is soluble in ether but not soluble in aqueous sodium hydroxide?

Question 2 options:

	ArOH
	Ar
	ArCOOH

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When you have a two-layer mixture of water and tert-butyl methyl ether, what physical property of these liquids assures you that the ether is the top layer?

Question 4 options:

low density was my answer was

You perform each extraction twice, first with 1 mL and second with 0.15 mL. Why is the second extraction necessary?

Question 8 options:

	several small extractions is better than one large one
	to remove any orgnaic material contaninating tube 2
	to remove any remaining neutral compound

7. Which of the following reactions is not favorable?

Question 7 options:

	ArCOOH + NaOH â ArCOO^-Na⁺ + H₂O
	ArOH + NaHCO₃ â ArO^-Na⁺ + CO₂ + H₂O
	ArCOOH + NaHCO₃ â ArCOO^-Na⁺ + CO₂ + H₂O

9.Why is phenol more acidic than an aliphatic alcohol?

Question 9 options:

	Its conjugates baseâs negative charge is localized on the oxygen
	Phenols have a stronger O-H bond
	Only the phenol can form hydrogen bonds
	Its conjugated base is stabilized by resonance

Which aqueous base reacts with a carboxylic acid but not with phenol? Why?

Question 10 options:

	Sodium bicarbonate, it is a weaker base and will only react with strong acids
	Sodium hydroxide, it is a strong base and will only react with strong acids
	Sodium bicarbonate, it is a weak base and will only react with weak acids
	Sodium hydroxide, it is a strong base and will only react with weak acids

CHEM120 Lecture 10: CHEM 120 Lecture 10: Types of Acid:Base Reactions

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