A concentration cell is constructed by using the same half-reaction for both the

Question

A concentration cell is constructed by using the same half-reaction for both the cathode and anode. What is E^infinity, for a concentration cell that combines silver electrodes in contact with 0.10 M silver nitrate and 0.00003 M silver nitrate solutions? (E^infinity = +0.80 V for Ag/Ag^+) +0.21 V +0.59 V +0.80 V -0.21 V +1.01 V When an acetic acid solution is titrated with sodium hydroxide, the slope of the titration curve (pH vs, volume of NaOH added) increases when sodium hydroxide is first added. This change shows that, nothing is happening during this part of the titration, the reaction is very slow during this part of the titration, a more concentrated solution of NaOH needs to be present to initiate the reaction, acetic acid is being converted to sodium acetate, the pH is not affected until all the acetic acid is consumed. When 10.5 g KBr(s) dissolves in 125 g of water at 24.2 degree C, the final temperature of the solution comes to 21.1 degree C. Assume that the heat capacity of the solution is roughly 4.18 J/(g middot degree C). What is the molar enthalpy of solution of potassium bromide (119 g/mol)? +19.9 kJ/mol +167 kJ/mol +1.76 kJ/mol +67.6 kJ/mol +18.4 kJ/mol Consider the equilibrium CO(g) + 2 H_2(g) reversible CH_3OH(), for which delta H degree = -128.5 kJ/mol and delta G degree = -29 kJ/mol at 298 K. Estimate the equilibrium constant at 313 K. 2.0 times 10^4 1.4 times 10^5 1.7 times 10^6 3.4 times 10^5 1.1 times 10^4 What is the pH of a 0.010 M acetic acid solution?(K_a for acetic acid is 1.76 times 10^-5.) 2.00 4.74 2.74 3.38 6.74 How much energy is needed to change the temperature of 275 grams of lead from 10.0 degree C to 95.0 degree C [C_p = 26.7 J/(mol middot degree C)] 35.5 J 113 J 3010 J 7340 J 23, 400 J The freezing point of ammonia (NH_3, 17.04 g/mol) is - 77.73 degree C. In an experiment, 367.2 grams at - 77.73 degree C is used to cool 250.0 grams of liquid NH_3 from 25.00 degree C to the freezing point. Assume specific heat capacity of liquid NH_3 is 4.742 J/(g middot degree C). What is the enthalpy of fusion of amn 2.894 kJ/mol -2.894 kJ/mol 5.652 kJ/mol -5.652 kJ/mol 0.3315 kJ/mol

Explanation / Answer

1) E0cell = 0 =E0cathode - E0anode

Ecell = E0cell - 0.0592 / 1 (log [Ag+ anode] / [Ag+ cathode] )

Ecell = -0.0592 log (0.00003 / 0.1) = +0.21 V

2) On adding NaOH in HCl solution neuralization starts.

So the concentration of H+ starts decreasing, which will increas pH of solution

reaction will be

CH3COOH + NaOH --> CH3COONa + H2O

Answer: acetic acid is converted to sodium acetate

3) Mass of KBr dissolved = 10.5 grams

Change in energy = Mass of solution X specific heat X change in temperature

Energy =( 125+10.5) X 4.18 X (24.2-21.1) = 1755.81 Joules / 10.5 grams

So energy for 1 gram = 1755.81 / 10.5 Joules

So energy for one mole or 119 grams = 119 X 1755.81 / 10.5 Joules = 19899 Joules = 19.899 KJ / mole = +19.9 KJ / mole

4) The Delta G value is not clear

We will use

Delta G = -RTln K = -2.303 X 8.314 X 10^-3 X ln (K)

5) [H+] = (Ka X concentration of acid)^1/2

[H+] = (1.76 X 10^-5 X 0.01)^1/2 = 4.19 X 10^-4

pH = -log[H+] = 3.38

6) Energy = Mass X specfic heat X change in temperature

1 mole of lead = 207 grams

Specific heat = 26.7 / 207 = 0.129 J / g

Energy = 275 X 0.129 X (95-10) = 3015.75 Joules Or 3010 Joules approx

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