HMN Item 1921

Part A

A 2.52 g lead weight, initially at 11.0 ∘C, is submerged in 8.15 g of water at 52.3 ∘C in an insulated container.

What is the final temperature of both the weight and the water at thermal equilibrium?

Part B

A silver block, initially at 60.0 ∘C, is submerged into 100.0 g of water at 25.1 ∘C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 27.3 ∘C.

What is the mass of the silver block?

Vapor Pressure of pure ethanol is 40.0 torr at 19 degrees C

3.42g of sugar (C12H22O11, non-volatile, non-electrolyte) is added to 50.0 mL of ethanol (C2H6O, 0.79 g/mL, melting point = -114 degrees C, Kf = 1.99 degrees C/m)

a. Calculate the vapor pressure of the sugar/ethanol solution @ 19 degrees C.

b. Calculate the melting point of the sugar/ethanol solution.

A mixture of 20.6g of phosphorus (P) and 79.4 chlorine (Cl2) reacts completely to form phosphorus trichloride (PCl3) and phosphorus pentachloride (PCl5).

(a) true or false: the bond angels of PCl3 and PCl5 are identical.

(b) what mass of PCl3 forms under the conditions described above?

(c) an analysis of a phosphorus and chlorine containing compound found that it was 30.40% phosphorus. is it one of the two products formed in this reaction? why pr why not?

Consider the titration of 80.0 mL of 0.0200 M NH₃ (a weak base; K_b = 1.80e-05) with 0.100 M HBrO₄. Calculate the pH after the following volumes of titrant have been added:

(a) 0.0 mL (d) 12.0 mL

(b) 4.0 mL (e) 16.0 mL

(c) 8.0 mL (f) 17.6 mL

correctly list the molecules in order of increasing boiling point (from lowest to highest)?

a.)CH3CH2CH2-OH

b.)CH3CH2CH2CH3

c.)CH3CH2-OH

I know the the answer wold be b,c,a but I don't understand why

Given the following acids or bases. 1) H2PO4 -2 2) CH3NH3 a. Write the reactions for each of the above b. Write the K expressions for the reactions and look up the K for each of the above. c. What is the conjugate of each of the above? (there may be more than one) d. Write the reaction for the conjugate interacting with water. e. Write the K expressions for the reactions that involves the conjugate and calculate the value of the K.

Find the effective nuclear charge for the 2s electrons in the Lithium atom. How much does each 1s electron shield the 2s electron from the nucleus?

Calculate the solubility (in mol/L) of lead(II) chloride, PbCl2, at 25 degrees celsius. Ksp = 1.59 x 10^-5

You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa = 4.20) and 0.220 M sodium benzoate. How much of each solution should be mixed to prepare this buffer?

a) mL of benzoic acid

b) mL of sodium benzoate

2. A mixture weighing 42.500 g contains 7.500 g NH4Cl, 19.650 g SiO2. With the remainder being NaCl. Find the percent by weight of each component. Show your calculations.

Calculate the [H3O+] of the following polyprotic acid solution: 0.135 M H3C6H5O7.

Express your answer using two significant figures.

Calculate the pH of this solution

Express your answer to two decimal places.

pH Dependence of Drug Absorption lab

1. Calculate the amount of Na₂HPO_{4 *} 7H₂O ( in grams) needed to make 50 mL of a 0.40 M solution.

2. Calculate the amounts of Na₂HPO₄ and NaH₂PO₄ (in grams) needed to prepare 200 mL of a buffer with pH=8.25 so that the sum of concentrations of HPO₄^2- and H₂PO₄^- ions is 0.5 M. pK_a1=2.12, pK_a2=7.21, pK_a3= 12.38

* on this problem I think you use the Henderson-Hasselbalch equation, but after that I'm lost.

3. Write the equation for the ionization of 3-aminophenol. Would this substance be more soulble in water at pH=2 or pH= 8? Would you expect this substance to be absorbed into the blood stream in the stomach or the instestines?

4. How does the initensity of the spot on the silica sheet relate to the solubility of the drug in the aqueous phase?

Please explain the the problems!!

A charge neutral macrocyclic ligand having four donor atoms froms a red, diamagnetic complex of Ni(II). The counter ions for this complex is the very weak Lewis base, ClO4-. When ClO4- is replaced by thiocyanate, violet complex forms.

a. Draw the structures of the red and violet complexes such that thier geometires can be decerned based only on your drawings.

b. Draw the d-orbital slitting diagrams of the red and violet complexes such that the relative energies of the orbitals in the two complexes can be compared.

c. Wse your orbital diagrams to show were the d electroms reside in each complex. Explain your electron configurations.

d. describe an experiment that you could do to test whether your predicted electron configurations are reasonable. Show what the results of this experiment would be for the d electron configureation that you showed in part c