How to make 100 mL of 100mM of Tris HCl and 100 mL of 100mM of Tris Base. Follow the pH of the resulting combined solution as it is heated from 0 to 50 degrees Celsius.

You don't specify the pH, so know one can help you with this one.

Well neither did my teacher that's why I'm confused to begin with.

I don't believe the pH is absolutely necessary; however, if it is wouldn't it be pH = pKa for TRIS. Since these are equal amounts of equal concentrations then (base) = (acid) and pH = pKa + log 1 = pKa.

Prepare the base by the following:
mols TRIS base = M x L = 0.100 x 0.100 = ?
So weigh g TRIS = mols x molar mass and you should have the base (you're weighing the base).

To make the acid, duplicate what you did for the base, then add mols HCl = mols base. If you don't have a standard HCl solution you will need to prepare one and add the exact amount, probably with a buret, of HCl to neutralize the base. You will want to be careful in your calculations since the HCl will be a solution you are adding and the volume may not exceed 100 mL.

TRIS buffers usually have a pH between 7 and 9, with TRIS having a pka value of 8.1. HCl is usually added to decrease the pH of the buffer to somewhere close to 7, which makes it a TRIS HCl buffer; it is usually only called TRIS HCl when the HCl has been added. This looks like an experimental protocol for a lab class, where you are investigating the effect of temperature change on the pH of the buffer and/or enzyme activity for a molecular or biochemistry lab course. I agree with Dr. Bob222: you do need a standard HCl solution to neutralize the TRIS base. And when you usually refer to TRIS-HCl, you are referring to the buffer with TRIS and HCl already added-- that is why I said you need the pH. The experimental protocol that Dr. Bob222 gave you is probably what the instructor meant when you were asked how to prepare both components for the buffer. And I should have read your question a little bit more closely before answering.

Best

I should have said TRIS-HCl is added to decrease the pH, not HCl. You want a slight change in the pH of the solution, not a rapid change. Adding HCl will cause you to miss the pH by too much, and is difficult to obtain the desired pH. TRIS base by itself usually has a pH above 10, and TRIS HCl has a pH below 5. However, equal quantities of the two should give you a pH of 8.1, which is the pka of the TRIS buffer.

Thanks for that information but how do you do a pH vs Temp graph for this? Because, I need to do the calculations and a graph of pH vs Temp? (Even if it's just an example or formulas it'd be very helpful and well appreciated.)

Charlotte,

It is just a simple Y vs X graph.

The pH is the dependent variable and is plotted on the y-axis, and the temperature is the independent variable and is plotted on the x-axis. For example, at say 63 degrees, the pH is 8.4. You will find 63 degrees on the y-axis, and find 8.4 on the x-axis and plot your point. You will do this for all of your reading for the experiment. Afterwards, you will make an equation for the line, in slope intercept form and determine the R^2 value. There are valuable resources on the internet that can help you make an equation for the line and determine the R2 value for your chart.