A 5.65 −g sample of a weak acid with Ka=1.3×10−4 was combined with 4.80 mL of 5.90 M NaOH and the resulting solution was diluted to 750 mL. The measured pH of the solution was 4.25.

A student reacts 81g of salicylic acid with 14 mL of acetic anhydride producing 2g of acetyl salicylic acid. What is the percent yield of the reaction?

What mass of ammonium chloride should be added to 2.50 L of a 0.145 M NH3 in order to obtain a buffer with a pH of 9.65?

Determine the pH of each solution.

Dissociation Constants at 25 ∘C

a) 0.21 M KCHO2

b) 0.21 M CH3NH3I

c)0.21 M KI

A battery is constructed from these two half reactions:

            i.   VO²⁺   +   2 H⁺ + e-   → V³⁺   + H₂O        E^o = 0.337 V vs SHE

            ii.   TiF₆^{2 ̶}   +   4 e-   →   Ti(s) + 6 F ^̶                           E^o = ̶ 1.191 V

(a) (0.2 pt) Which half reaction is in the anode compartment?   Circle one:     vanadium rxn      titanium rxn

(b) Which half reaction is in the cathode compartment? Circle one:    vanadium rxn      titanium rxn

(c) Write the balanced chemical equation for the overall battery reaction.

(d) Show the shorthand notation for representing this particular battery:

(e) Calculate the E^o of the battery.

Q: Discuss why matrix effects can be important in AAS.

Q: How can I determine if matrix effects were significant in a sample (let say a tap water).

The osmotic pressure of a solution containing 2.16 g of an unknown compound dissolved in 175.0 mL of solution at 25 ºC is 2.65 atm. The combustion of 25.05 g of the unknown compound produced 58.02 g CO2 and 19.80 g H2O. The compound contains only carbon, hydrogen, and oxygen.

What is the molecular formula of the compound?

Express your answer as a chemical formula

how many ml each are needed to make a buffer with 0.12 M HC3H5O3- (KA=1.4 *10^-4) AND 0.15 NaC3H5O3 that has a pH=3.77

SHOW ALL WORK

1) The air pollutant NO is produced in automobile engines from the high-temperature reaction, N2 (g) + O2 (g) ⇌ 2 NO (g); Kc = 1.7 × 10-3 at 2300K . If the initial concentrations of N2 and O2 at 2300 K are both 1.4 M, what are the concentrations of NO, N2, and O2 when the reaction mixture reaches equilibrium? Show your work (20 points).

2) For each of the following equilibria, use LeChatelier’s principle to predict the direction of reaction when the volume is increased. (15 points)

(a) CO(g) + H2(g) ⇌ C(s) + H2O(g)

(b) 2H2(g) + O2 (g) ⇌ 2 H2O(g)

(c) Fe2O3(s) + 3 H2(g) ⇌ 2Fe(s) + 3 H2O(g)

3) Will the concentration of NO2 increase, decrease, or remain the same when the equilibrium of the exothermic reaction, NOCl(g) + NO2(g) ⇌ NO2Cl (g) + NO(g) is disturbed by the following changes? (15 points)

(a) adding NOCl

(b) adding NO

(c) Removing NO

(d) Adding argon

(e) addition of a catalyst

4) Calculate [H+] of a solution prepared by dissolving 4.25 grams of lithium hydroxide (24 g/mole) in water (18 g/mole) to give 350.0 mL of solution. (12 points) Kw = 1.0 × 10-14

5) Lactic acid (C3H6O3), which occurs in sour milk and foods such as sauerkraut, is a weak monoprotic acid. The [H+] of a 0.10 M solution of lactic acid is 4.57 × 10-3. What is the value of Ka for lactic acid? (16 points)

6) Write a chemical reaction for each of the following ions reacting with water. Demonstrate with this reaction whether they give neutral, acidic, or a basic solution. (16 points)

(a) F-

(c) NH4+

(d) K(H2O)6+

(e) SO32-

7) Calculate the percent dissociation of 0.10 M hydrazoic acid (HN3; Ka = 1.9 ×10-5) in the presence of 0.10 M HCl, and explain if this dissociation is more, the same, or less than if the HCl was not present. (16 points)

Write a balanced equation for the oxidation of methanol with KMnO₄ in acidic solution; show how you balanced the reaction using half-reactions.

The Ka of a monoprotic weak acid is 4.40 × 10-3. What is the percent ionization of a 0.185 M solution of this acid?

For the following reaction, Kc = 255 at 1000 K. CO(g)+Cl2(g)⇌COCl2(g) A reaction mixture initially contains a CO concentration of 0.1490 M and a Cl2concentration of 0.180 M at 1000 K.

a) What is the equilibrium concentration of CO at 1000 K?

b) What is the equilibrium concentration of Cl2 at 1000 K? c

) What is the equilibrium concentration of COCl2 at 1000 K?

Is sodium hypochlorite insoluble or soluble?

If the rate law for the clock reaction is: Rate = k [ I-] [ BrO3 -] [H+] A clock reaction is run with the following initial concentrations: [I-] [BrO3-] [H+] [S2O32-] 0.002 0.008 0.02 0.0001 The reaction time is 28 seconds Calculate k in the rate law:

Also:

Rate = k [ I-] [ BrO3 -] [H+] A clock reaction is run at 19 ºC with the following initial concentrations [I-] [BrO3-] [H+] [S2O32-] 0.002 0.008 0.02 0.0001 Then the experiment is repeated at 33 ºC, the rate constant k is found to be 2.7 times larger. Calculate the activation energy

Find the pH during the titration of 20.00 mL of 0.1820 M nitrous acid, HNO2 (Ka = 7.1 ✕ 10-4), with 0.1820 M NaOH solution after the following additions of titrant. (

a) 0 mL

(b) 10.00 mL

(c) 15.00 mL

(d) 19.00 mL

(e) 19.95 mL

(f) 20.00 mL

(g) 20.05 mL

(h) 25.00 mL