Question

how many grams of sodium phosphate are needed to make 626 ml of a 0.571 m solution? report your answer to one place past the decimal point.

Explanation:

Step1: Calculate the number of moles of sodium phosphate

The formula for molarity \(M=\frac{n}{V}\) (where \(n\) is the number of moles and \(V\) is the volume in liters).
Given \(M = 0.571\space M\) and \(V=626\space mL=626\times10^{- 3}\space L\)
\(n = M\times V=0.571\times626\times10^{-3}\)
\(n = 0.571\times0.626 = 0.357446\space mol\)

Step2: Calculate the molar mass of sodium phosphate \((Na_3PO_4)\)

The molar mass of \(Na\) is \(22.99\space g/mol\), \(P\) is \(30.97\space g/mol\), and \(O\) is \(16.00\space g/mol\)
\(Molar\space mass\space of\space Na_3PO_4=3\times22.99 + 30.97+4\times16.00\)
\(=68.97+30.97 + 64.00\)
\(=163.94\space g/mol\)

Step3: Calculate the mass of sodium phosphate

The mass \(m=n\times molar\space mass\)
\(m = 0.357446\times163.94\)
\(m\approx58.6\space g\)

Answer:

\(58.6\space g\)