1.)A student prepares a potassium dichromate solution by dissolving .5263 gram of dry solid potassium dichromate in enough water to make 1000.mL of solution. What is the concentration of dichromate ions in the resulting solution?

2)A student measures 10.00 mL of an unknown solution of Fe2+ into an Erlenmeyer flask and dilutes with 90 mL of 1.0 M hydrochloric acid. She then titrates this sample with the solution prepared in question#1 .If 29.50 mL of the potassium dichromate solution is needed to reach the endpoint, what is the concentration of Fe2+ in the original unknown solution.

Basic chemical structures of the organisms Concept map

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A 360.0?mL buffer solution is 0.160M in HFand 0.160M in NaF.

What mass of NaOH could this buffer neutralize before the pH rises above 4.00?

If the same volume of the buffer was 0.370M in HF and 0.370M in NaF, what mass of NaOHcould be handled before the pH rises above 4.00?

Titration Curve of unknown Acid

Molarity of NaOH =.172

1. Your unknown acid is one of the following: oxalic acid (H2C2O4*2H20, pKa1=1.27, pKa2=4.27), citraconic acid (C5H6O4, pKa1=2.29, pKa2=6.15), or Maleic Acid (C4H4O4, pKa1=1.92, pKa2=6.09). These acids are classified as diprotic. Calculate the molar mass for your acid using the average mass from trials 1 and 2 and the average volume at the first equivalence point; then redo the calculation using the average mass from trials 1 and 2 and the average volume at the second equivalence point.

2. Using the average molar mass at the second equivalence point that you calculated in question 1, and your average values of pKa1 and pKa2, indentifiy your unknown acid. Explain.

Prepare a 2.00 L of a 2.00 M buffer of pH 4.35. You can use citric acid (pka 3.09, 192.1 g/mol) and NaOH (10.0 M). Calculate how much of each reagent (and water) to make the buffer (show work).

The answers are:

Citric acid: 786 g, NaOH: 514 mL, water: 1.486 L

How do you get to these results?

For 530.0 mL of a buffer solution that is 0.155 M in CH3CH2NH2 and 0.145 M in CH3CH2NH3Cl, calculate the initial pH and the final pH after adding 0.020 mol of HCl.

The combination of sodium chlorite and acetic acid forms hypochlorous acid (HOCl), which is the active ingredient in this reaction. Draw the arrow pushing mechanism of your reaction, using HOCl as reagent.

1. For the following, predict the products (if any). If there is no reaction, write “no rxn”. For the

questions where reaction occurs, write:

 balanced molecular equation

 balanced complete ionic equation

 balanced net ionic equation

 classify the reaction as either precipitation or acid base resulting in a gas

Include phases for all species.

a) NaI(aq) + Pb(ClO4)2(aq)

b) Ba(NO3)2(aq) + (NH4)2SO4(aq)

c) HCl(aq) + NaHSO3(aq)

d) Cu(CH3COO)2(aq) + Rb2CO3(aq)

e) aqueous potassium carbonate + hydrobromic acid

f) Mg(NO3)2(aq) + Zn(CH3COO)2(aq)

g) aqueous silver perchlorate + aqueous magnesium bromide

h) NH4Cl(aq) + KOH(aq)

A chemist is working with a formic acid � formate ion buffer system.

HCHO₂(aq) + H₂O(l) <=> CHO₂^-(aq) + H₃O⁺(aq) with K_a = 1.7�10^-4

One liter of the buffer contains 0.745 moles of formic acid and 0.385 moles of formate ion. What is the pH of the buffer? (Answer to 3 significant figures, no units.)

______________________________________________________

Solid sodium hydroxide (6.83 grams) is added to one liter of the formic acid � formate ion buffer described in the previous question. Assume the total volume has not changed significantly once the strong base has dissolved. What is the new pH of the buffer? (Answer to 3 significant figures, no units.)

What is the pH of the solution that results from micing 75 mL of 0.50 M NH₃(aq) and 75 mL of 0.50 HCL(aq) at 25 xC? (K_b for NH₃ = 1.8x 10^-5)

a. 0.60

b 2.67

c. 4.74

d. 4.93

e. 9.26

If 10.0 ml of 0.100 M strong base is titrated with 25.0 ml of 0.100 M strong acid, what is the pH of the resulting solution?

You and your lab partner are studying the rate of a reaction, A + B --> C. You make measurements of the initial rate under the following conditions:

(a) Which of the following reactant concentrations could you use for experiment 3 in order to determine the rate law, assuming that the rate law is of the form, Rate = k [A]^x [B]^y? Choose all correct possibilities.

[A] = 7.0 and [B] = 1.2[A] = 4.2 and [B] = 1.2[A] = 2.8 and [B] = 3.6[A] = 5.6 and [B] = 1.2[A] = 1.4 and [B] = 2.4[A] = 1.4 and [B] = 3.6[A] = 2.8 and [B] = 2.4[A] = 2.8 and [B] = 1.2

(b) For a reaction of the form, A + B + C --> Products, the following observations are made: tripling the concentration of A increases the rate by a factor of 3, doubling the concentration of B has no effect on the rate, and doubling the concentration of C increases the rate by a factor of 4. Select the correct rate law for this reaction from the choices below.

Rate = k[A][B][C]Rate = k[A][C]     Rate = k[A]² [C]Rate = k[A][C]²Rate = k[A]² [C]²Rate = k[A]³ [C]Rate = k[A][C]³
(c) By what factor will the rate of the reaction described in part (b) above change if the concentrations of A, B, and C are all halved (reduced by a factor of 2)?

The rate will be the original rate multiplied by a factor of  .

4 Fe(s) + 3 O₂(g) → 2 Fe₂O₃(s), ΔH = -1652 kJ

(a) How much heat is released when 4.03 mol iron is reacted with excess O₂?
. kJ

(b) How much heat is released when 1.47 mol Fe₂O₃ is produced?
. kJ

(c) How much heat is released when 1.17 g iron is reacted with excess O₂?
kJ

(d) How much heat is released when 12.70 g Fe and 2.24 g O₂ are reacted?
kJ

Consider the titration of a 100mL of 0.100 M HCN by .100M NaOH. (Ka for HCN is 6.2x10^-10) Calculate the pH after 50.0 mL of .100M NaOH has been added

With relevance to Organic Chemistry and acids and bases, can somebody teach me everything there is to know about pka?