Question

What mass of lithium phosphate would you mass to make 2.5 liter of 1.06 M lithium

phosphate solution?

Answer 1

Approximately
`3.06 * 10^(2)\; \rm g` (approximately
`306\; \rm g`.)

Step-by-step explanation:

Calculate the quantity
`n` of lithium phosphate in
`V = 2.5\; \rm L` of this
`c = 1.06\; \rm M = 1.06\; \rm mol \cdot L^(-1)` lithium phosphate solution.

`\begin{aligned}n &= c \cdot V\\ &= 2.5\; \rm L * 1.06\; mol \cdot L^(-1)\\ &= 2.65\; \rm mol\end{aligned}`.

Empirical formula of lithium phosphate:
`\rm Li_3PO_4`.

Look up the relative atomic mass of
`\rm Li`,
`\rm P`,and
`\rm O` on a modern periodic table:

• 
  `\rm Li`:
  `6.94`.
• 
  `\rm P`:
  `30.974`.
• 
  `\rm O`:
  `15.999`.

Calculate the formula mass of
`\rm Li_3PO_4`:

`M(\rm Li_3PO_4) = 3 * 6.94 + 30.974 + 4 * 15.999 = 115.79\; \rm g \cdot mol^(-1)`.

Calculate the mass of that
`n = 2.65\; \rm mol` of
`\rm Li_3PO_4` formula units:

`\begin{aligned}m &= n \cdot M \\ &= 2.65\; \rm mol * 115.79\; \rm g\cdot mol^(-1) \\ &\approx 3.06 * 10^(2)\; \rm g \end{aligned}`.