6. Competencias evaluativas: En esta competencia evaluativa se trabajó en los siguientes desempeños pertenecientes a los estándares 1 y 3:
5.4.3. Propuesta de formación docente en competencias en TIC
w h ich does not lie n e a r the cu rve . The o th e r exception was Rao and Subram anya^^^, who d e te rm in e d lo g jS by p o la ro g ra p h y.
Table 32. T herm o dyn a m ic p a ra m e te rs fo r p ro to n a tio n of a sparaginate and g lu ta m in a te in 3. OOM (N a )C lO ^a t 25°C aspa ra g ina te g lu ta m in a te - K . i 53,10 55.03 - ^ ^ 1 , 2 14. 76 15.55 67.86 70.58 - A H o.1 50. 50 50.86 5 .1 0 4 .4 2 - ^ « 0 . 2 55. 60 55.28 8 .9 P 1 4 .0 ^ 2 3 2 .4 3 7 .4 K 2 4 1 .3 5 1 .4
A g^ and A H ° a re expressed in u n its of kJ m o l and A s ° u nits
-1 -1
a re J m o l K . The p a ra m e te rs A g^ A n ° ^ and A ^ r e fe r to
the p ro to n a tio n o f the am ine s ite , the A ^
,
p a ra m e te rs r e fe r to the 2, , ^ 2 9,1 34 ,1 63 - A ca rb o xyla te s ite and the A a
Ü, 2 q u a n titie s a re o v e ra ll fig u re s . The e ffe ct of adding a -C H ^ group to asparaginate, m aking g lu ta m in a te, is re fle c te d in g lu ta m in a te ’ s s lig h tly la rg e r -* A g^ , - A h°
a ris e s fro m an a p p ro x im a te ly 20% in cre a se in the entro p y o f p ro to n a tin g g lu ta m in a te as com pared to a sparaginate, w h ich o ccu rs because the g lu ta m in a te lig a n d is thought to possess m o re w a te r o f aquation w h ich is shed upon p ro to n a tio n . A consequence o f A h ^ fo r g lu ta m in a te being ro u g h ly equal to
A
fo r asparaginate is that andA
fo r g lu ta m in a te f i t the A g^ - v e rsu s A S ° - p lo t^ ^ ^ (fig u re 19).F o r c a rb o xyla te p ro to n a tio n A g (or pK) is e s s e n tia lly entropy
' 164 — "h
dependent . Hansen et a l suggested that RCO H e xists in s o lu tio n as
I o
an io n p a ir and so A h app ro xim a te s to zero and does not depend on the
n a tu re o f R . T lius p ro to n a tio n is an e le c tro s ta tic phenomenon and th is is re fle c te d in A 8^ because the num ber of w a te r m olecules in vo lve d depend f a r m o re upon the charges of the ions concerned than upon the v a rie ty of groups being protonated. Iz a tt produced evidence fo r such concepts in the fo rm of lin e a r p lo ts of A G ^ against A 8° at ze ro io n ic stre n g th . The slope of th e ir p lo ts was s ig n ific a n tly close to that p re d ic te d by
166
B je r r u m ’ s the o ry of e le c tro s ta tic in te ra c tio n s (-243K com pared to -2 1 8 K ). The data w h ich have been co m p ile d at 3. 00M (N a)C lO ^ a re fe w e r, b u t these p a ra m e te rs can also be said to lie n e a r the lin e of slope -2 1 8K .
F ig u re 19 shows the re s u lts co m p ile d at 3. 00M (Na)ClO ^. The s o lid lin e has slope -2 1 8K and the b ro ke n lin e has slope -243K .
V-.-
The am ine p ro to n atio n s m ay be co ntra ste d w ith p ro to n a tin g carbo^yrlate groups because (i) am ine p ro to n a tio n is enthalpy dependent,
I