Given the following thermodynamic reactions: CaO (s) + Cl2 (g) ---> CaOCl2 delta H° = -110.9 KJ/ H20 (l) + CaOCl2 (s) + NaBr (s) ---> 2NaCl (s) + Ca(OH)2 (s) + Br2 (l) delta H° = -60.2 KJ/ Ca(OH)2 (s) ---> CaO (s) + H2O (l) delta H° = +65.1 KJ. Calculate the value of delta(Δ)H° (in kilojoules) for the reaction 1/2 Cl2 (g) + NaBr (s) ---> NaCl (s) +1/2 Br2 (l)

Lithium Nitrogen reacts to form Li3N. A 4.0g sample of lithium is reacted with 2.5g of nitrogen. What weight of what substance remains unreacted?

3.Phosphate-buffered saline (PBS) is a buffer solution commonly used in biological research. Most formulations contain a mixture of KCl and NaCl buffered to a pH of 7.40 using phosphate-containing compounds.

a.The following reagents are available in your lab. Choose the correct reagents and calculate the volumes necessary to prepare exactly 5.0 L of a phosphate buffer with a pH of 7.40.

                                               0.100 M H3PO4 0.150 M Na2HPO4

                                               0.200 M KH2PO4 0.120 M Na3PO4

b.Commercial PBS solutions are typically prepared by dissolving solid reagents in water and then adjusting the pH to 7.40 using HCl. The formulation shown below is for the preparation of 10.0 L of a PBS solution. What is the pH of this solution and how many moles of HCl must be added to

adjust the pH to 7.40?

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Question

1. When NO2 is bubbled into water, it is completely converted to HNO3 and HNO2 according to the reaction shown below. Calculate the pH and the molar concentrations of all dissolved species (H3O+, OH–, HNO2, HNO3, NO2–, and NO3–) in a solution prepared by bubbling 4.601 g NO2 through 2.00 L of water.

2NO2(g) + H2O(l) → HNO3(aq) + HNO2(aq)

2. 12.6-g sample of Na2A (molar mass = 126 g/mol) is dissolved enough water to produce 1.00 L of solution. The pH of this solution is 9.85 and the equilibrium concentration of H2A is 1.0 × 10–12 M. Determine the values of pKa1 and pKa2 for H2A

3.Phosphate-buffered saline (PBS) is a buffer solution commonly used in biological research. Most formulations contain a mixture of KCl and NaCl buffered to a pH of 7.40 using phosphate-containing compounds.

a.The following reagents are available in your lab. Choose the correct reagents and calculate the volumes necessary to prepare exactly 5.0 L of a phosphate buffer with a pH of 7.40.

                                               0.100 M H3PO4 0.150 M Na2HPO4

                                               0.200 M KH2PO4 0.120 M Na3PO4

b.Commercial PBS solutions are typically prepared by dissolving solid reagents in water and then adjusting the pH to 7.40 using HCl. The formulation shown below is for the preparation of 10.0 L of a PBS solution. What is the pH of this solution and how many moles of HCl must be added to

adjust the pH to 7.40?

4. Consider the potentiometric titration of 25.0 mL of 0.200 M selenious acid (H2SeO3) with 0.250 M NaOH.

a. Identify the primary selenium-containing species present at each point in the titration (A – E) shown below. Then sketch the titration curve, identifying points A – E. Make sure to appropriately label the axes.

One millimole of Ni(NO3)2 dissolves in 210mL of a solution that is .500M in NH3.

(a) What is the initial concentration of Ni(NO3)2 in the solution?

------> The answer to (a) is .00476 M. I just can't figure out part (b)

(b) What is the equilibrium concentration of Ni^2+(aq) in the solution?

HINT: The Ni^2+ forms a hexammonia complex: Ni(NH3)6^2+. Kf = 5.5 x 10^8.

Oxalic acid, H2C2O4 has acid dissociation constants Ka1 = 5.9 � 10^2 and Ka2 = 6.4 � 10^5. What is the pH after 20.00 mL of 0.0500 M NaOH is added to 5.00 mL of 0.2000 M H2C2O4?

The Answer is 2.8 but I don't know how to get there

Assuming that the smallest measurable wavelength in an experiment is 0.570 fm , what is the maximum mass of an object traveling at 745 m ⋅ s^-1 for which the de Broglie wavelength is observable?

When an excited electron in a hydrogen atom falls from n=7n to n=2, a photon of ultraviolet light is emitted. If an excited electron in an He+ ion falls from n=5, which energy level must it fall to (n1) for ultraviolet light of a similar wavelength to be emitted?

A 2.100×10−2 M solution of glycerol (C3H8O3) in water is at 20.0∘C. The sample was created by dissolving a sample of C3H8O3 in water and then bringing the volume up to 1.000 L. It was determined that the volume of water needed to do this was 999.1 mL . The density of water at 20.0∘C is 0.9982 g/mL.

a.) Calculate the molality of the glycerol solution. Express your answer to four significant figures and include the appropriate units.

b.)Calculate the mole fraction of glycerol in this solution. Express the mole fraction to four significant figures

c.)Calculate the concentration of the glycerol solution in percent by mass. Express your answer to four significant figures and include the appropriate units.

d.)Calculate the concentration of the glycerol solution in parts per million. Express your answer as an integer to four significant figures and include the appropriate units.

A gaseous mixture consists of 76.0 mole percent N₂ and 24.0 mole percent O₂ (the approximate composition of air). Suppose water is saturated with the gas mixture at 25°C and 1.00 atm total pressure, and then the gas is expelled from the water by heating. What is the composition in mole fractions of the gas mixture that is expelled? The solubilities of N₂ and O₂at 25°C and 1.00 atm are 0.0175 g/L H₂O and 0.0393 g/L H₂O, respectively.

A buffer with a pH of 3.90 contains 0.15 M of sodium benzoate and 0.30 M of benzoic acid. What is the concentration of [H ] in the solution after the addition of 0.050 mol of HCl to a final volume of 1.4 L?

Measuring Radiation

Part A

At a distance of 40 ft , an ionizing radiation source delivers 7.0 rem of radiation. How close could you get to the source and still have no biological effects?

Express your answer to two significant figures and include the appropriate units.

Part B

A nurse administered 2.50 mL of a radioisotope solution that has an activity of 165 μCi/mL . What total dose of the radioisotope did the patient receive?

Express your answer to three significant figures and include the appropriate units.

The following enthalpy and entropy changes are known for the reactions shown at 298 K.

Part a

Which of the these two metals, Zn or Cu, should dissolve in 1 M acid solution? Explain your answer.

Part B -

Calculate E^o for the Zn reaction. Show work to support your answer.

Part C -

Which of the two reactions has an equilibrium constant that increases with temperature? Explain your answer.

Part D -

Would you have expected that both reactions would have had a negative change for delta S? How can you explain delta S is less than zero for these reactions?

A holding tank with capacity 5000 litres initially contains 1500 litres of 25 mM NaCl solution. a) What is the final concentration of NaCl (expressed in mM) if an additional 3000 litres of 25 mM NaCl solution is pumped into the tank? b) Instead of (a), if 3000 litres of water are added to the tank, what is the final concentration of NaCl (expressed in mM)? c) Instead of (a) or (b), if an additional 500 litres of 25 mM NaCl solution plus 3000 litres of water are added, what is the final concentration of NaCl:

iv. Expressed as ppm? (ppm means g per 106 g of solution) You can assume that the density of the solution (NaCl + water) is the same as the density of water – this assumption is appropriate since this is a dilute solution. Assume density of water to be 1 g/cm3 .

Note: mM means milli-molar (1 mM means 1 milli-mol/liter)

The generic reaction

2A?B

has the following rate laws:

forward reaction:reverse reaction:rate=kf[A]2rate=kr[B]

where kf is the rate constant for the forward reaction and kr is the rate constant for the reverse reaction. At equilibrium, the two rates are equal and so kf[A]2=kr[B]. The equilibrium constant for a reaction is related by the law of mass action to the rate constants for the forward and reverse reactions:

Kc=[B][A]2=kfkr

Formation of nitrosyl bromide

Nitrosyl bromide, NOBr, is formed in the reaction of nitric oxide, NO, with bromine, Br2:

2NO(g)+Br2(g)?2NOBr(g)

The reaction rapidly establishes equilibrium when the reactants are mixed.

A.

At a certain temperature the concentration of NO was 0.400 M and that of Br2 was 0.265M . At equilibrium the concentration of NOBr was found to be 0.250 M. What is the value of Kc at this temperature?

Express your answer numerically.

In organic chemistry lab we just completled a "Lidocaine Synthesis". I have some questions to clarify before we take the in class exam.

1. Based on apperence and melting point; how can we validate if the crystals are pure lidocaine?

2. When using the seperatory funnel in extraction, we washed the organic layer with water and would shake then drain the aqueous layer out. After a couple of washes with water, we then use HCL to extract and collect this aqueous layer seperatley. Following the extraction with HCL we then again washed the organic solution with water. Any of the washes with water were collected then combined at the end of using seperatory apparatus. Why would we wash the oganic layer with water again after using HCL? Does it yeild more product?

3. What compund were we dissolving in the aquoues extract?