Suppose you have an aqueous solution prepared by dissolving $0\mathrm{.}047$ mol of in $1$ L of water $().$ This solution is not a buffer, but suppose you want to make it into one. How many moles of solid must you add to this aqueous solution to make it into:

A buffer of pH $7\mathrm{.}21$

n$=$ mol

A buffer of pH $6\mathrm{.}21$

n $=$ mol

A buffer of pH $8\mathrm{.}21$

n $=$ mol