Questions & Answers

Question about acetate buffer and what happens when HCl is added to such a solution

Debra ask:How do I attack this problem?
I want to compare the effect of adding 1mmol of HCL to 100 ml of 0.2M acetate buffer at two different starting pH's.
(pKa of acetate buffer =4.7Initial pH = 4.7Initial pH = 5.7Thank you

Hi Debra,

There is both a short and long answer to your question. The short answer is that at pH=4.7 you are muchcloser to the equivalence point of your buffer (pH 4.7 when its a CH3COOHCH3COO- buffer) and at that pH the additionof HCl will cause a much larger change in pH than at pH=5.7.

However, you can calculate (this is the long answer) how much pH changes by doing some fairly simplecalculations. Since the explanation is not short I've made a separate webpage answering your question.It is named acetate buffer.The answer is also found as a pdf document named acetate buffer. The Excel spreadsheet showing allthe calculations is shownhere.

Question about glucose and ionic strength

Anonymous ask:what would be the ionic strenth of say 100mM Glucose? where there is no charge?

Dear Anonymous,

When there is no charge there is no contribution to the ionic strength. Ionic strength only counts charge ions.So, for any standard calculation glucose is not considered charged - and do not contribute to the overall ionicstrength of the solution. You can refer to the page about ionic strength.

Buffers BackgroundAs shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3 abuffer has the capability of keeping pH within a certain and narrow range even if an excessof hydrogen ions H+ or hydroxide ions OH- are added.In this particular page I will elaborate a bit on why buffers actually have the capabilities ...

pKa and Ka Background informationThe Ka value is a value used to describe the tendency of compounds or ions to dissociate. The Ka value is also called the dissociationconstant, the ionisation constant, and the acid constant.Topic: Equilibriums The pH scale The ...

Gases - the ideal gas law explained Chemical compounds in aqueous solutions are fairly easy to handle as their quantities can either be expressed in weight such as grams or kilos, moles perliter (molarity) or moles per kg (molality).Topic: pKa & Ka The basics ...

pH meter pH strips BackgroundpH meters have been used since 1936 when they were invented by the Danish company Radiometer.In contrast to many other measuring devices pH meters do not measure concentrations, rather they measure activities. Tobe more specific the pH meter does not measure the concentration of hydrogen ions.pH meters are used to ...