How many grams of the bromide salt of the conjugate acid must be combined with how many grams of the weak base, to produce 1.00 L of a buffer that is

79.1g of weak base must be combined with 56.0g of conjugate acid

Explanation:

that is 1.00 M in the weak base?

The weak base is C5H5N with a pKa of 5.17 (Ka=6.7×10-6)and a desire pH of 5.63

The equilibrium of the weak base is with the bromide salt of the conjugate acid is:

C5H5N(aq) + H2O(l) + Br- ⇄ C5H5NHBr(aq) + OH-(aq)

Where Kb = Kw / Ka = 1x10⁻¹⁴ / 6.7x10⁻⁶

Kb = 1.49x10⁻⁹ is defined as:

Kb = 1.49x10⁻⁹ = [C5H5NHBr] [OH-] / [C5H5N]

Where [OH-] = 10^-(14- pH) = 10^-(14- 5.63) = 4.255x10⁻⁹M

[C5H5N] = 1.00M

Replacing:

1.49x10⁻⁹ = [C5H5NHBr] [OH-] / [C5H5N]

1.49x10⁻⁹ = [C5H5NHBr] [4.255x10⁻⁹M] / [1.00M]

[C5H5NHBr] = 0.35M

In 1L the moles of C5H5NHBr are 0.35 moles

Mass C5H5NHBr: 160.0118g/mol

0.35 moles * (160.0118g / mol) =

56.0g of C5H5NHBr are necessaries

The mass of C5H5N is -79.1g/mol-:

1.00moles * (79.1g/mol) =

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.