The titration curve of a weak base with a strong acid is shown to the right. Whi

Question

The titration curve of a weak base with a strong acid is shown to the right. Which region or regions correspond to solutions having the greatest buffering capacity? A) 3.4 B) 2.5 C) 2 D) 4 F) 5 48. What is the pH of a solution that contains 0.25M benzoic acid, HC_3H_5O_2, and 0.75M sodium benzoate, NaC_3H_5O_2? K_a(benzoic acid) = 6.3times10^-5 A) 3.72 B) 4.68 C) 10.28 D) 9.32 E) 6.35 49. Calculate DeltaGdegree (in kJ) at 350.0degreeC for the reaction below, using the data provided in the table. 2NO_2(g) rightarrow N_2O_4(g) A) -413 B) 1.10times10^5 C) 4.37 D) 52.4 E) -64.0 50. Consider the information in the table below; calculate the equilibrium constant for the reaction at 298 K. H_2(g) +I_2(g) 2 HI(g) A) -880 B) -0.37 C) 0.37 D) 0.99 E) 880

Explanation / Answer

47 ) the greatest buffer capacity at point 2. thee fore the option B is correct,

buffer capacity is measure of efficiency of buffer in resistance to change in pH,

48 ) WE CAN CALCULATE THE pH By using the following formual,

pH= Pka + log (A-/HA),

we know that pka = -log Ka ,

so first we can calculate the pka from Ka as,

Ka= 6.3*10-5,

pka = - log 6.3*10-5,

pka= 4.20 , by putting this value to the equation,

pH= 4.20 + LOG [C6H5COO-Na+]/[C6H5COOH],

pH= 4.20 + LOG [0.75/0.25],

pH= 4.20 + 0.4771 ,

pH= 4.677 (OPTION B is correct),

49 ) delta G0 FOR REACTION CAN BE CALCULATED AS ,

2 NO2 (g) -------> N2O4 (g)

delta G0 = delta H0- T*delta S0 ,

delta H0= sumation Hf product -summation Hf reactants,

delta H0= ( 9.16- 33.18) ,

delta H0 = - 24.02 ,

delta S0= ( delta S PRODUCTS- DELTA S REACTANTS),

delta S0 = (304.3-240.1 ),

delta S0 = 64.2 ,

NOW , by putting the values to the equation,

delta G0= delta H0 - T* delta S0,

delta G0= -24.02 - (623 K*64.2) ( 350 DEG C +273= 623 K)

delta G0= - 24.02 -( 39996.6),

delta G0= - 413 THERE FOR E OPTION A is correct

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