CHE 1302 Lecture Notes - Lecture 12: Equilibrium Constant, Hydrofluoric Acid, Rice Chart

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20 Dec 2017

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Acids and bases examples 2 ions as acids and bases. Predict whether each of the following salts will form acidic, basic, or neutral solutions* Ch3nh3br from the parent base from the parent acid. Solution character neutral basic acidic neutral basic acidic basic. The anion is basic (the 4th and 7th examples weren"t done in class - just a couple of extra examples. For the last one, it should serve as a reminder that the cation can sometimes be 2+!) * the cation of the salt always comes from the parent base and the anion always comes from the parent acid. To determine the parent acid: the parent acid is the anion plus a proton (it"s a conjugate base so give it back its proton ). ph of a salt containing by a weakly acidic cation. First dissolve the salt; then determine how each ion reacts with h2o. dissolution: +(aq) + h2o is of the form acid.

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

Observations In columns 3 and 4, record the color and intensity seen. In columns 5 and 6, determine if the substance is an acid or a base, and if the substance is ionic. For the last column, determine which chemical species is acting as an acid or base.

Data Table 1: Acids and Bases Acting in Water
Well	Substance	1drop BTB	Plus 1 drop of substance	Acid or base (Q1)	Ionic? Y/N (Q2)	Species acting as acid or base (Q3)
1	NaHCO3
2	CH3COOH
3	HCL
4	Na2CO3
5	H2SO4
6	CH3COONa
7	NaOH
8	HNO3
9	NaHSO4
10	NH3
11	H3PO4
12	NaH2PO4
13	Na2HPO4
14	Na3PO4
15	NaHSO3

Data Table 2: Following Acid/Base neutralization reactions
Well #	1 Drop of Each	Observation	+2 Drops Acid	Observation	+2 Drops Base	Observation
1	BPB + NaOH		HCl		NaOH
2	BPB + NaOH		H2SO4		NaOH
3	BPB + NaOH		CH3COOH		NaOH
4	BPB + NaOH		H3PO4		NaOH
5	BPB + Ca(OH)2		HCl		Ca(OH)2
6	BPB + Ca(OH)2		H2SO4		Ca(OH)2
7	BPB + Ca(OH)2		CH3COOH		Ca(OH)2
8	BPB + Ca(OH)2		H3PO4		Ca(OH)2
9	BPB + NH3		HCl		NH3
10	BPB + NH3		H2SO4		NH3
11	BPB + NH3		CH3COOH		NH3
12	BPB + NH3		H3PO4		NH3

Please note here if any of the other starting materials is other than a clear, colorless solution.

Data Table 3: Investigating Odor as a Means of Indicating Neutralization.
Substance(s)	Odor
2 Drops of HCl in Well #1
1 Drop of Ammonia on Swab
Swab with Ammonia & HCl

Data Table 4: Investigating Evaporation as a Means of Indicating a Neutralization Reaction.
Reaction Mixture	Observation (When Wet)	Observation (When Dry)
HCl + NaOH
CH3COOH + NH3
HNO3 + NaOH

PART 5: Mini-Experiments

1. Use BTB to classify four household products as acidic or basic. Possible substances to test include home cleaning products, glass cleaner, liquid detergent, bleach, soft drinks, liquid from food items, etc. Remember to:

a. Hypothesis (What you think will happen and why) or purpose:

b. Method used to test your hypothesis:

c. Data and Observations Put your data and observations in the space below. You can include pictures that you âdraw.â

d. Conclusions

2. Find one common, highly colored substance that can be used as an acid-base indicator.

Possible substances include fruit/vegetable juice or products, inks, food coloring, flower

petals, etc. If using fresh fruit, veggies, or flowers, crush the substance with a little water or

rubbing alcohol to extract the colored pigments. If red cabbage is available, it makes a superb

acid-base indicator. Then use a few drops of the colored extract as the indicator. Test four

more household products using the freshly made acid-base indicator. Remember to:

a. State a hypothesis or purpose.

b. State the testing method.

c. Use the prepared indicator to test four substances known to be acids or bases from either the LabPaq or home materials and record results.

d. State conclusions in terms of the hypothesis or purpose.

Questions

A. Review the substances used in Part 1. Determine whether each substance contains an acid or a base based on the BTB results. Place answers to this question in column 6 of Data Table 1.

B. Review the responses to Question 3. The anion that is produced in the dissociation of the compound goes on to react with the water. Identify the anion product in each reaction. Place the formulas for these species into column 7 of Data Table 1. If the substance is not ionic and thus does not dissociate, then list the substance in column 7, just as it appears in column 1.

C. For each ionic species in Data Table 1, write the equation showing the dissociation of the compound in water. Hint: thereâs one for each line provided below.

a. NaHCO3 Ã Na

+ HCO3

Review the responses to Question 3. The anion that is produced in the dissociation of the compound goes on to react with the water. Identify the anion product in each reaction. Place the formulas for these species into column 7 of Data Table 1. If the substance is not ionic and thus does not dissociate, then list the substance in column 7, just as it appears in column 1.

D. Write the reaction of each acid or base the substance listed in column 7 with water.

Acids: Bases:

a) HCO - + H-OH Ã H CO

+ OH-

3 2 3

1. What is produced in each and every reaction of an acid with water?

2. What is produced in each and every reaction of a base with water?

E. Review the results in Data Table 2. For each reaction mixture, write the reaction equation describing the acid/base neutralization reaction:

2) 2NaOH + H2SO4 Ã 2H2O + Na2SO4

F. Define the term âneutralizationâ and provide an example of a neutralization equation. List the three ways used in this lab to detected neutralization.

G. Define the term âsalt,â and provide an example.

H. Review Data Table 3. What happened when the two chemicals were mixed? What indicates that conclusion? What reaction took place?

I. Review Data Table 4. What happened when the solution mixtures on the glass slide were heated? Describe the process that took place.

J. In Part 4, for HCl + NaOH, what is left on the slide after heating? Provide the formula. What is the common name of this substance?

a Safari allä»¤ 4:15 PM * 19% Laboratory Experiments 267 standardize knob until the pH meter indicates the exact pH of the buffer solution. Wait 5 s to be certain that the reading remains constant. Once you have standardized the pH meter, do not readjust the standardize knob. Turn the function knob to standby. Carefully lift the electrodes from the buffer and rinse them with distilled water. The pH meter is now ready to use to measure pH. 2. Effect of Acid and Base on the Buffer pH Pour half (32 mL) of the buffer solution you prepared above into another 150-mL beaker. Label the two beakers 1 and 2. (CAUTION: Concentrated HCL can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Pipet 1.0 mL of 6.0 M HCl into beaker 1, mix, and then measure the pH of the re- sultant solution and record the pH. Remember to rinse the electrodes be- tween pH measurements. (CAUTION: Sodium hydroxide can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Similarly, pipet 1.0 mL of 6.0 MNaOH into beaker 2, mix, and then measure and record the pH of the resultant solution. Calculate the pH values of the original buffer solution, the values after the additions of the HCl and NaOH. How do the measured and calculated values compare? Dispose of the chemicals in the designated receptacles. Before beginning this experiment in the laboratory, you should be able toan swer the following questions: PRE LAB QUESTIONS 1. Define BrÃ¸nsted-Lowry acids and bases. 2. Which of the following ions will react with water in a hydrolysis reac- tion: Nat, Ca2+, Cu2+,Zn2*,F, So,Br? For those ions in question 2 that undergo hydrolysis, write net ionic equations for the hydrolysis reaction. The Ka for HCN is 4.9 Ã 10-10 What is the value of Kb for CN-? 3. 4. 5. What are the conjugate base and conjugate acid of H2PO4? 6. From what acid and what base were the following salts made: CaSO4, NH Br, and BaCl2? 7. Define the term salt Tell whether 0.1 M solutions of the following salts would be acidic, neutral, or basic: BaCl2, CuSO4, (NH4) S04, ZnCl2, NaCN. If the pH of a solution is 8, what are the hydrogen- and hydroxide-ion 8. 9. concentrations? The pH of a 0.1 M MCI (M* is an unknown cation) was found to be 4.7 Write a net ionic equation for the hydrolysis of M and its correspond ing equilibrium expression Kp. Calculate the value of Kp What is the pH of a solution that is 0.10 M HC2H302 and 0.20 M NaC2H3O2? Ka for acetic acid 1.8 Ã 10-b 10. 11.

CHE 1302 Lecture Notes - Lecture 12: Equilibrium Constant, Hydrofluoric Acid, Rice Chart

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