Pyridine, c5h5n, is a weak base with kb = 1.5 × 10-9. what amount of pyridinium chloride, c5h5nhcl, must be added to 1.00 l of 0.250 m c5h5n, in order to produce a buffer having ph 5.00? assume no change in volume.

We should add 0.3785 moles of pyridinium chloride

Explanation:

Step 1: Data given

Kb = 1.5 * 10^-9

pKb = -log(1.5 * 10^-9) = 8.82

Molarity of C5H5N = 0.250 M

Volume of the buffer = 1.00 L

pH =5

pOH = 14 -5 = 9

Step 2: Calculate [C5H5NHCl]

pOH = pKb + log [C5H5NCl] /[C5H5N]

9 = 8.82 + log [C5H5NCl] /[C5H5N]

0.18 = log [C5H5NCl] /[C5H5N]

[C5H5NCl] /[C5H5N] = 1.514

[C5H5NCl] = 1.514 * 0.250

[C5H5NCl] = 0.3785 M

pOH = 8.82 + log (0.3785/0.25) = 9

If pOH = 9 then pH is 5

Step 3: Calculate number of moles of C5H5NHCL

moles = Molarity / volume

moles = 0.3785 M / 1 L

moles = 0.3785 moles

We should add 0.3785 moles of pyridinium chloride

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6