What is the pH in a titration of 125 mL of 0.45 F sulfurous acid (H2SO3) with a 1.23 M solution of sodium hydroxide before any base is added?

An unknown solid is entirely soluble in water. On addition of dilute HCl, a precipitate forms. After the precipitate is filtered off, the pH is adjusted to about 1 and H2S is bubbled in; a precipitate again forms. After filtering off this precipitate, the pH is adjusted to 8 and H2S is again added; no precipitate forms. No precipitate forms upon addition of (NH4)2HPO4. The remaining solution shows a yellow color in a flame test. which might be present, might be absent, definitely absent?

You have a stock of a DNA solution at 1.2mg/ml, the DNA fragment being 980bp in length. How do you prepare a dilution of this DNA that has a concentration of 0.5uM ?

Some of the reactions for coal gasification are as follows:

Reaction 1:    C(s) + H₂O(g) « CO(g) + H₂(g)                 ΔH^o = 131.3 kJ/mol

Reaction 2:    CO(g) + H₂O(g) «CO₂(g) + H₂(g)                 ΔH^o = -41.2 kJ/mol

Reaction 3:    CO(g) + 3H₂(g) O(g) « H₂O(g) + CH₄(g) ΔH^o = -205.9 kJ/mol

1.Write the equilibrium constant expression for reaction 3.

2. For all three reactions, predict the way the equilibrium will shift in response to an decrease in pressure. EXPLAIN.

3. For all three reactions, predict the direction in which each equilibrium shifts in response to an increase in reaction volume. EXPLAIN.

4a. Write the ionization of HNO₃(aq) using Bronsted-Lowry definition. Identify conjugate acid/base pairs.

b. Find the pH of a .10 M HNO₃(aq) solution.

5a. Write the ionization of HClO₂(aq) using Bronsted-Lowry definition. Identify conjugate acid/base pairs.

b. Find the pH of a .10 M HClO₂ (aq). Ka=1.2 x 10^-2.

6. Explain why you set up your calculation the way you did in questions 4 and 5.

5. The formation constant of the silver-ethylenediamine complex, Ag(NH2CH2 CH2NH2)+, is 5.0 x 104. Calculate the concentration of Ag+ in equilibrium with a     0.10 M solution of the complex. (Assume no higher order complexes).

6. What would be the concentration of Ag+ in (problem 5) if the solution contained also 0.10 M ethylene diamine (NH2CH2 CH2NH2).

What is concentration of sodium nitrate if 25.5 g of sodium carbonate (MM = 105.99 g/mol) are added to a 500 mL of a 2.50 M iron (III) nitrate solution? Assume to change in volume and don't include units in your answer.

3Na₂CO₃ (s) + 2Fe(NO₃)₃ (aq) → Fe₂(CO₃)₃ (s) + 6NaNO₃ (aq)

   M NaNO₃

In a practical session, Hubert was asked to prepare potassium peroxide, K2O2 (s). He measured 3.910 g of potassium metal and burnt it in a container of oxygen gas with a mass of 2.560 g.

a) Write a chemical equation with state symbols for the reaction between potassium and oxygen.

b) Deduce which reactant, potassium or oxygen, is limiting.

c) Calculate the amount, in gram, of K2O2 (s) produced in the reaction.

d) It was found that the mass of K2O2 (s) obtained in the experiment was 3.609g. Calculate the percentage yield of K2O2 (s).

A 25.0 mL sample of 0.100 M HC2H3O2 (Ka = 1.8 x 10^-5) is titrated with a 0.100 M NaOH solution. What is the pH after the addition of 12.5 mL of NaOH?

1. Instrumentation is a key aspect of chemistry and specifically spectroscopy for organic chemistry. Why is spectroscopy the preferred technique in your opinion? How does this make the field of organic chemistry possible? In regards to mass spectra why is this technique so useful? Why is it so versatile with the various detectors it can be coupled with?

2. Studying about chemical separation techniques how do you see chemical separations in everyday life? How do those separations take place and why are they important? What other chemistry and physics principles do we take advantage of with all separations and why does that matter to us as organic chemist? Why does it matter to you and future or current career goals?

Balance each of the following redox reactions occurring in acidic aqueous solution.

art A

K(s)+Cr3+(aq)→Cr(s)+K+(aq)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Part B

Cd(s)+Cu+(aq)→Cd2+(aq)+Cu(s)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Part C

BrO−3(aq)+N2H4(g)→Br−(aq)+N2(g)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Balance each of the following redox reactions occurring in basic solution.

Part A

H2O2(aq)+ClO2(aq)→ClO−2(aq)+O2(g)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Part B

Al(s)+MnO−4(aq)→MnO2(s)+Al(OH)−4(aq)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Part C

Cl2(g)→Cl−(aq)+ClO−(aq)

Express your answer as a chemical equation. Identify all of the phases in your answer.

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Wine Chemistry

You are given the task of analyzing a sample of grapes to determine if a vineyard is ready for harvesting

1a. The concentration of tartaric acid is critical. This can be determined by a titration experiment with 0.1M NaOH and a color Indicator (phenolphthalein. The reaction is as follows:

Tartaric acid + 2 NAOH + colorless -> 2 H0+ 2 Na" + Tartrate

You have a 0.010L sample of grape juice and after adding 0.018 L of NaOH solution the color turns pink What is the "Titratable acidity" in g/L of tartaric acid in the grape juice sample?

Steps: volume of NaOH solution moles of NaOH > moles of tartaric acid grams of tartaric acid. Then divide grams of tartaric acid by volume (L) of grape solution

1b. Acidity goes down as grapes ripen. If the answer to the previous problem is less than 7 g/L then the grapes are ready. Based on your answer are they ready?

Sza. The ather important consideration is the concentration of sugar (which increases as grapes ripen). The appropriate sugar level is about 200 g/L What is the molarity of sugar in ripe grape Juice? (molar mass of sugar is 180 g/mole).

26. Amore commonly used unit in wine-making is Brix 1 brix = 10g/Of sugar. It your grape juice sample has a brix reading of 10, is it ready to harvest?