# Need help with titrations and buffers

• bohemian
In summary: I have two homework questions that don't make sense at all. I don't really know what formulas to use exactly. Here they are:1. Molar mass of a certain metal carbonate, MCO3, can be determined by adding an excess of HCl acid to react with the carbonate and then "back-titrating" the remaining acid with NaOH.a. Write an equation for these reactionsb. In a certain experiment, 20.00 ml of 0.800M HCl were added to a O.1022 gram sample of MCO3. The excess HCl required 5.64 ml of 0.1000M NaOH for neutralization. Calculate the molar mass of the carbonate and
bohemian
I have two homework questions that don't make sense at all. I don't really know what formulas to use exactly. Here they are:

1. Molar mass of a certain metal carbonate, MCO3, can be determined by adding an excess of HCl acid to react with the carbonate and then "back-titrating" the remaining acid with NaOH.
a. Write an equation for these reactions
b. In a certain experiment, 20.00 ml of 0.800M HCl were added to a O.1022 gram sample of MCO3. The excess HCl required 5.64 ml of 0.1000M NaOH for neutralization. Calculate the molar mass of the carbonate and identify M.

and

2. Calculate the volume in ml of 6.0 M NaOH that must be added to 0.500 L of a buffer made of 0.0200M acetic acid and 0.0250M sodium acetate, in order to obtain a final pH of 5.75.

Any help to get me started on these would be greatly appreciated. My homework is due on Wed. so if anyone could reply back before then, that would be great. Thank you.

I can help u with the first.From the notation,i'd suspect that the metal ion is divalent so the reactions would go

$$MCO_{3}+2HCl\rightarrow MCl_{2}+CO_{2}\uparrow+H_{2}O$$

$$NaOH+HCl\rightarrow H_{2}O+NaCl$$

Daniel.

Did u do the arithmetics...?It's really useful to use mols all the way.

Daniel.

## 1. What is a titration and why is it important?

A titration is a laboratory technique used to determine the concentration of a solution by reacting it with a known concentration of another solution. It is important because it allows scientists to accurately measure the concentration of a substance, which is crucial in many scientific experiments and processes.

## 2. How do I perform a titration?

To perform a titration, you will need a burette, a known concentration solution, and the solution you want to determine the concentration of. Start by filling the burette with the known concentration solution and recording the initial volume. Then, slowly add the known solution to the other solution until the reaction reaches its endpoint. Record the final volume and use the difference to calculate the concentration of the unknown solution.

## 3. What is a buffer and why is it used in titrations?

A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It is used in titrations to maintain a constant pH throughout the reaction, which is important for accurate results. Without a buffer, the addition of acid or base could drastically change the pH and affect the endpoint of the titration.

## 4. How do I prepare a buffer solution?

To prepare a buffer solution, you will need to mix a weak acid or base with its conjugate salt. The ratio of acid to salt will determine the pH of the buffer solution. You can also adjust the pH by using different weak acid/base and salt combinations. It is important to use precise measurements and calculations to prepare a buffer solution with the desired pH.

## 5. What are some common sources of error in titrations?

Some common sources of error in titrations include inaccurate measurements of solutions, improper calibration of equipment, and contamination of solutions. It is also important to ensure that the reaction has reached the endpoint and that the pH is accurately measured. To minimize these errors, it is essential to carefully follow the steps of the titration procedure and to use precise and calibrated equipment.

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