Calculate Moles of CH3NH2 Needed for pH 9.55: Buffer Solution

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In summary, to calculate the moles of CH3NH2 needed for a pH 9.55 buffer solution, use the Henderson-Hasselbalch equation to determine the concentration and then use the formula moles = concentration x volume. The pKa value for CH3NH2 is 10.64, which can be found in a reference table or using a pH calculator. To prepare a buffer solution with a pH of 9.55 using CH3NH2, mix it with its conjugate acid in a specific ratio determined by the Henderson-Hasselbalch equation. A buffer solution is needed for pH 9.55 to maintain a stable pH, as small changes in acidity or basicity can cause large changes in pH.
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alingy2
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You want to have a ph of 9.55 with a buffer. How many grames of CH3NH3ClO4 would you add to 800 ml of 0.258 M CH3NH2 to do this. Assume volume remains constant. Kb for methylamine is 4.2x10^-4.

My answer is 320g. Can anyone check this please? I have an exam on buffers very fast. You would do me a great favor.
I used Henderson to find concentration of methylamine required. Then the number of moles and grams.
 
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I got 319 g, close enough.
 

1. How do you calculate the moles of CH3NH2 needed for a pH 9.55 buffer solution?

To calculate the moles of CH3NH2 needed, you will first need to determine the concentration of the buffer solution. This can be done by using the Henderson-Hasselbalch equation: pH = pKa + log([base]/[acid]). Once you have the concentration, you can use the formula moles = concentration x volume (in liters) to find the moles of CH3NH2 needed.

2. What is the pKa value for CH3NH2?

The pKa value for CH3NH2, also known as methylamine, is 10.64. This value can be found in a reference table or by using a pH calculator.

3. How can you prepare a buffer solution with a pH of 9.55 using CH3NH2?

To prepare a buffer solution with a pH of 9.55 using CH3NH2, you will need to mix a weak base, such as CH3NH2, with its conjugate acid in a specific ratio. This ratio can be determined using the Henderson-Hasselbalch equation: pH = pKa + log([base]/[acid]). Once you have the ratio, you can use it to calculate the amount of CH3NH2 and its conjugate acid needed to make the buffer solution.

4. Why is a buffer solution needed for pH 9.55?

A buffer solution is needed for pH 9.55 because it helps maintain a stable pH in a solution. Without a buffer, small changes in acidity or basicity can cause a large change in pH. In this case, the buffer solution with a pH of 9.55 will resist any changes in pH, making it useful for experiments or processes that require a specific pH level.

5. Can I use any other weak base instead of CH3NH2 for a pH 9.55 buffer solution?

Yes, you can use other weak bases besides CH3NH2 for a pH 9.55 buffer solution. Some examples include NH3, NH4OH, and C2H5NH2. However, the specific ratio of weak base to conjugate acid needed may differ depending on the pKa value of the weak base used. It is important to use a weak base with a pKa value close to the desired pH of the buffer solution for optimal results.

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