How many moles of CH₃NH₃Cl need to be added to 200.0 mL of a 0.500 M solution of CH₃NH₂ (Kb for CH₃NH₂ is 4.4 × 10⁻⁴) to make a buffer with a pH of 9.70?

Answer : The moles of weak base needed to added is, 0.871 mol.

Explanation : Given,

Concentration of weak base = 5.00 M

Volume of solution = 200.0 mL

pH = 9.70

First we have to calculate the value of .

The expression used for the calculation of is,

Now put the value of in this expression, we get:

Now we have to calculate the value of pOH.

Now we have to calculate the moles of weak base .

Now we have to calculate the moles of conjugate base or salt .

Using Henderson Hesselbach equation :

Now put all the given values in this expression, we get:

Therefore, the moles of weak base needed to added is, 0.871 mol.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.

i belive it is water