•OWL HOMEWORK

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CH3CO2H(aq) + NaOH(aq)

1 2 3

11% 12%

77%1. CH3CO2H2

+(aq) + NaO(aq)

2. CH3CO2-(aq) + H2O(l) + Na+(aq)

3. CH4(g) + CO2(g) + H2O(l)

HCN(aq) + NH3(aq)

1 2 3

88%

5%7%

1. NH4+(aq) + CN-(aq)

2. H2CN+(aq) + NH2-(aq)

3. C2N2(s) + 3 H2(g)

The pH Scale

Quantitative measure of solution acidity

Remember solution concentration:

[NaCl]=0.25M means 0.25 moles of NaCl are in 1L of solution

solventL

solutemolesMolarity

1

#

How much of a 1.oM HCl solution should I add to neutralize 1.0L of 0.1M NaOH?

1.0L0.1M NaOH

1 2 3 4 5

5%

21%

8%

24%

42%1. 1.0 mL2. 10.0 mL3. 100.0 mL4. 1.0 L5. 10.0 L

The pH Scale

In pure water, some molecules ionize to form H3O+ and OH-

H2O + H2O OH– + H3O+

In acidic and basic solutions, these concentrations are not equal

acidic: [H3O+] > [OH–]

basic: [OH–] > [H3O+]

neutral: [H3O+] = [OH–]

The pH Scale

pH scale= measure of [H3O+]pH < 7.0 = acidicpH > 7.0 = basicpH = 7.0 = neutral

Measure of H3O+ concentration (moles per liter) in a solution

As acidity increases, pH decreases

The pH Scale

The pH scale is logarithmic100100 101022 log(10log(1022) = 2) = 21010 101011 log(10log(1011) = 1) = 111 101000 log(10log(1000) = 0) = 00.10.1 1010–1–1 log(10log(10–1–1) = –1) = –10.010.01 1010–2–2 log(10log(10–2–2) = –2) = –2

pH = –log [HpH = –log [H33OO++]]

Logs- a quick review

log N = a 10a = N

Example

log 4 = 0.602 100.602 = 4

The pH Scale

pH = –log [HpH = –log [H33OO++]]

pH if [HpH if [H33OO++] = 10] = 10–5–5? 10? 10–9–9??

Acidic or basic?Acidic or basic?

pH if [HpH if [H33OO++] = 0.000057 M?] = 0.000057 M?

Finding [H3O+] from pH

[H[H33OO++] = 10] = 10-pH-pH or [H or [H33OO++] = log] = log-1-1 (-pH) (-pH)

Finding the inverse log (or log Finding the inverse log (or log -1-1)of a number )of a number on your calculator:on your calculator:

Enter the number, press the inverse (inv) or shift button, Enter the number, press the inverse (inv) or shift button, the press the log button (it might be labeled 10the press the log button (it might be labeled 10xx))

What is [HWhat is [H33OO++] if pH = 8.6?] if pH = 8.6?

pH: Quantitative Measure of Acidity

Acidity is related to concentration of H+ (or H3O+)

pH = -log[H3O+]

[H3O+]= 10-pH = log-1(-pH)

pOH measures basicity

pOH=-log[OH-]

pH + pOH = 14

Precipitation Reactions

Solubility of Ionic Compounds

dissolving

How to determine if an ionic compound is soluble

Identify the two ions

Check the “solubility rules” Soluble ions with no “exceptions” never form

precipitates

If one of the ions is insoluble, the compound is insoluble

Make sure to check for “exceptions”

Example: K2CO3

If a reaction product is insoluble, it will form a precipitate

Examples

Soluble or Insoluble?

1. NaNO3

2. FeCl3

3. Fe(OH)3

4. BaSO4

5. AgNO3

6. AgCl

More Examples (on your handout- try at home)

Soluble or Insoluble?

7. K3PO4

8. Fe3(PO4)2

9. PbCl2

10. FeSO4

11. (NH4)2S12. PbS

When potassium chromate and barium nitrate react, which product precipitates?

1 2 3

57%

17%

26%

1. BaCrO4

2. KNO3

3. Both products are insoluble

Precipitation ReactionsNet Ionic Equations

Pb(NO3)2 + K2CrO4 ?

Pb(NO3)2 + KI ?

BaCl2 + KNO3