CHEM 2090 Lecture Notes - Lecture 8: Chemical Equilibrium, Lewis Acids And Bases, Alkalinity

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14 Dec 2016

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Chemical equilibrium= reflects a condition in which the forward and reverse rates for a process are equal (and opposite) Chemical equilibrium can be reached by either direction. Chapter 20: the properties of acids and bases. Acid base reactions are among the most common and important. Alkalinity scale poh poh = -log [oh-] stuff in [] is in m (concentrations) ph+poh=14. 00 neutral ph = 7. 0. Weak acids and bases only dissociate partially in water. The equilibrium equation does not include water (only aq substances) Ka = [h+ ][a ] /[ha] pka = log ka. The conjugate base is the base that results from the acid. The conjugate acid is the acid that results from the base. For a conjugate acid base pair pka + pkb = 14. 00. Neutral cations are the cations from strong bases and neutral anions are the anions of strong acids. Basic anions are the conjugate bases of weak acids.

Related Questions

QUESTION 1

Which of the following substances is most acidic?

		Cowâs milk - pH 6.6
		Apple juice - pH 3.0
		Tomato juice - pH 4.5
		Distilled water - pH 7.0

2 points

QUESTION 2

A buffer is a substance that converts:

Alkaline solutions to neutral solutions.

Acidic solutions to alkaline solutions.

Strong bases or acids to weak bases or acids.

Acidic solutions to neutral solutions.

QUESTION 3

How does a solution of pH 7 compare to a solution of pH 10?

		pH 7 has more OH^- ions
		pH 7 is more basic
		pH 7 has a higher pH
		pH 7 has more H⁺ ions

2 points

QUESTION 4

According to the Arrhenius Theory of acids and bases, a base is:

A substance that decrease the amount of hydroxide ions present.

A substance that increases the amount of hydroxide ions present when it is dissolved in water.

A substance that increase the amount of hydrogen ions present.

A substance that increases the amount of hydrogen ions present when it is dissolved in water.

QUESTION 5

Which of the following are true regarding acid-base titrations?

		They are used to determine the concentration of an unknown acid or base.
		The acid or the base must be a standard solution with a known concentration
		The standard solution is titrated into the chemical with the unknown concentration.
		All of the above are true regarding acid-base titrations.

2 points

QUESTION 6

Which of the following is not an example of a neutralization reaction?

HCl + NaOH NaCl +H₂O

2 NaOH + H₂CO₃ Na₂CO₃ +2 H₂O

H₂SO₄ + 2 NH₄OH (NH₄)₂SO₄ + 2 H₂O

2 AgNO₃ + Zn 2Ag +Zn(NO₃)₂

QUESTION 7

Which acid base theory defines an acid as a proton donor and a base as a proton acceptor?

		Arrhenius Theory
		Bronsted-Lowery Theory
		Conjugate Pairs Theory
		Lewis Theory

2 points

QUESTION 8

The Arrhenius Theory states that acid-base reactions create a solution composed of a water and a salt. This is because mixing an acidic and basic solution together yields:

A neutral solution

A solution with a pH at or near 7

Both A and B are correct

QUESTION 9

Which of the following correctly defines a standard solution?

		A solution which always has the same molecular geometry.
		A solution in which the concentration is precisely known.
		A solution in which the volume is precisely known.
		A solution which always has different levels of solutes and solvents.

2 points

QUESTION 10

Acids naturally present in food are generally safe to eat because they are usually:

		Concentrated
		Dilute
		Weak
		Strong

None of the above are correct

1. Determine the amount of solute in the following samples:

500 ml of 0.2 M KI (potassium iodide)

220 ml of 0.03 M H2SO4 (sulfuric acid)

2.5 l of 0.1 M MgNO3 (magnesium nitrate)

1 ml of 5 M HCl (hydrochloric acid)

This problem requires that you know what molarity (M) is. M (molarity) = # of moles of solutes / Liter of solution. You are given the volume. You should be able to obtain moles of solutes. Your answers can be in moles or grams (either one will be acceptable).

2. How many ml of 0.1 M HCl would be required to titrate 35 ml of 1 M NaOH to the end point?

This is an acid/base reaction.

1) First, write out the balanced chemical reaction for HCl + NaOH.

2) Second, figure out the number of moles of NaOH in 35 ml of 1 M NaOH.

3) How many moles of HCl is required for completely reacting with the moles of NaOH in Part 2).

3. What is the pH of a 0.03 M solution of the strong base NaOH?

1) This question requires that you know pH = - log [H₃O⁺], or simply as pH = - log [H⁺] (to make it easier).

2)So, you have to know how to use your scientific calculator to do log function (check Youtube).

3) This question also requires that you know: pOH = - log [OH^-].

4) This question also requires that you know: [H₃O⁺][OH^-] = 1.0 x 10^-14 or pH + pOH = 14

5) First step, determine the concentration of OH^- in 0.03M NaOH when it dissociates or breaks up into Na⁺ and OH^-.

6) This will give you [OH^-]. You can plug this into pOH = - log [OH^-] to get pOH.

7) Once you get pOH, then use (pH + pOH = 14) to get pH.

4. Balance the chemical reactions shown below and then write equilibrium expressions for each. All reactants and all products are in the gas phase.

CO + F₂ ------> COF₂

CH₄ + O₂ ------> CO₂ + H₂O

N₂O₄ -----> Br₂ + NO

BrNO -----> Br₂ + NO

1)This problem requires that you know how to balance chemical equations.

2)After you balance the equation, you need to know the equilibrium expression

5. Determine the oxidation states of each element comprising the following ionic compounds:

KClO₄

NaMnO₄

Sr(NO₃)₂

NaHCO₃

CH₄

CHEM 2090 Lecture Notes - Lecture 8: Chemical Equilibrium, Lewis Acids And Bases, Alkalinity

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