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?

Calculate the pH at the equivalence point in titrating 0.034 M solutions of each of the following with 0.093 M NaOH. (a) periodic acid (HIO4) pH = (b) hydrocyanic acid (HCN), Ka = 4.9e-10 pH = (c) arsenous acid (H3AsO3), Ka = 5.1e-10

5. A sample of N2 gas at 298 K and 1 atm. The diameter of N2 molecule is d = 3.6 × 10-10 m. (1) Calculate the collisions per second that one molecule of N2 make. (II) Calculate the mean free path 2 in meter. 6. An ideal gas has absorbed 900 J as a heat energy and the volume of the gas was decreased from 20 L to 10 L at constant external pressure of 5 atm. (1) The work done on the system (in J) in this process is: (II) The internal energy change (AU) of the system (in J) in this process is: 7. A cylinder with a piston contained 5 mole of helium (He). The system allowed to expand at constant pressure after adsorbing 25 kJ energy as a heat. (Knowing that Cy =12.47 J/mol.K) (1) Calculate AH (in J) for the process? (II) Calculate AU (in kJ) for the process?

Electrochemistry is the study of the conversion between chemical and electrical energy. Describe how oxidation-reduction reactions are used to make a battery, converting the chemical energy from the reactions to electrical energy.