Consider a protein in which a negatively charged glutamic acid side chain (pka=4.2) makes a salt bridge (ion-ion interaction) with a positively charged histidine side chain (pka=6.5).

part a. do you predict that this salt bridge will become stronger, become weaker, or be unaffected as ph increases from ph=6.9 to ph=7.5?

The salt bridge will be unaffected by the increase in PH

Explanation:the in introduction of salt bridge in a solution is to maintain a balance between the positive cations and the negatively charge glutamic acid.it does this by releasing positive ion to the glutamic acid solution and releasing negatively charged ions to the histine side of the arrangement.this because over time positive and negatively charged ions may build up at both ends respectively hindering flow of electrons .

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"