General Chemistry Answers

Which of the following species is trigonal bi-pyramidal?

A. AlH₄^-

B. PCl₄⁺

C. PCl₅

D. SnH₄

Which of the following pairs of quantum numbers is not possible (impossible) and why?

A. 1,2,3,-1/2

B. 2,1,0,1/2

C.1, 0, 0, -1/2

D. 5,4,0,+-1/2

E.3,1,0,+1/2

Which of the following does not contain covalent bonds?

A. Carbon(graphite)

B.Carbon(diamond)

C. HCl_(g)

D. NaCl_(s)

1,00 liter of solution A was prepared by dissolved 15,40 gram of 3,4−DHBA acid and 15,40 gram 3,5−DHBA acid on distilled water.

1,0 liter of solution B was prepared by dissolved 30,80 gram mixture of 3,4−DHBA acid and 3,5 – DHBA acid. pH of solution B is 2.40.

a) Calculate pH value of solution A.

b) How many gram of each acid (3,4−DHBA acid and 3,5 – DHBA acid) was used to prepare 1,0 liter of solution B.

c) Describe the method to prepare 1,00 liter of buffer solution with pH = 4,11 by using distilled water, solid 3,4−dihydroxybenzoic acid and solid sodium 3,4−dihydroxybenzoate. In this buffer solution: Ca + Cb = 1,00 M (Ca is 3,4−dihydroxybenzoic acid concentration; Cb is sodium 3,4−dihydroxybenzoate concentration).

Given by: M(DHBA) = 154 gam.mol−1 .

pKa 3,4− dihydroxybenzoic acid (3,4−DHBA) 4,48

pKa 3,5− dihydroxybenzoic acid (3,5−DHBA) 4,0

b) Given in the following electrochemical cell at 25o C:

(−) Cu çCu2+ ( 0.10 M) ççAg+ (0.10 M) çAg (+) (*)

How the voltage of cell will change (increase or decrease) when the following reagents be added? Shortly explaination. Assume the volume of anode/cathode solution does not change by addition of reagent.

-A small amount of NaCl onto solution at cathode of the cell (*).

-Addition EDTA solution onto solution at anode of the cell (*).

c) Solution A was prepared by mixing 10,0 mL NH3 solution with concentation of 0,500 M and 10,0 mL AgNO3 solution with concentration of 0,020 M.

i) Calculate pH value of solution A and equilibrium concentration of Ag+ .

ii) Replace the solution in cathode of the above cell (cell (*)) by solution A, in this case, the voltage of cell will change. Determine the new value of cell voltage.

Eo (Ag+ /Ag) = 0.799 ; Eo (Cu2+/Cu) = 0.337 ; bAg(NH3) + = 103,32; bAg(NH3)2 += 07,23; pKaNH4 +=9,24. Ignore hydroxo formation of Ag+ và Cu2+ ions

Limonene is a volatile liquid which smells of oranges. A teacher placed a beaker of limonene at the front of a classroom. At first, the students at the back of the classroom could not smell the limonene. After two minutes, the smell of limonene had spread throughout the classroom. The air in the classroom was still and calm. Explain these observations using the kinetic particle model.

Solution A contains H2S 0.10 M, solution B contains Fe(NO3)2 0.10 M. a) Calculate pH value of solution A and the equilibrium concentration of H2S; HS− and S2− in solution A. b) Mix 1.00 mL solution A and 1.00 mL solution B. In the resulting solution, the precipitate will form or not? Explain by calculation. c) Calculate the solubility of FeS in solution with pH = 3.0. Given by: H2S: pKa1 = 7.02; pKa2 = 12.90; pKS(FeS) = 17,2; *b(FeOH+ ) = 10−5.92

The structural isomers C₂H₅OH and CH₃OCH₃ would be expected to have the same values for which of the following? (Assume ideal beahviour)

A. Gaseous densities at the same temperature and pressure

B. Vapour pressures at the same temperature

C. Boiling points

D. None of the above

Choose compounds with covalent polar bonds:

A. Cl₂

B. ZnSO₄

C. NH₃

D.ZnO

Plot concentration time graphs for

a) First order reactions.

b) Second order reactions

c) Zeroth order reactions