To determine the grams of sodium phosphate in a solution, we start with the information given: a 0.550 molar sodium phosphate solution and a volume of 300 milliliters. The molecular mass of sodium phosphate is 163.94 grams per mole. The first step is to convert the volume from milliliters to liters, as molarity is defined in terms of liters. Since 1 milliliter is equal to \(10^{-3}\) liters, we convert 300 milliliters to liters:

\(300 \, \text{mL} = 300 \times 10^{-3} \, \text{L} = 0.300 \, \text{L}\)

Next, we use the molarity formula, which states that molarity (M) equals moles (n) divided by liters (L). Rearranging this gives us:

\(n = M \times L\)

Substituting the values we have:

\(n = 0.550 \, \text{mol/L} \times 0.300 \, \text{L} = 0.165 \, \text{mol}\)

Now that we have the number of moles of sodium phosphate, we can convert moles to grams using the molecular mass. The conversion is done using the formula:

\( \text{grams} = n \times \text{molecular mass}\)

Substituting the values:

\( \text{grams} = 0.165 \, \text{mol} \times 163.94 \, \text{g/mol} = 27.0501 \, \text{g}\)

When reporting the final answer, we must consider significant figures. The volume (300.0 mL) has 4 significant figures, while the molarity (0.550) has 3 significant figures. Therefore, we round our final answer to 3 significant figures:

Final answer: \(27.1 \, \text{g}\) of sodium phosphate.

In summary, when calculating grams from a solution's volume and molarity, remember to convert units appropriately, apply the molarity formula to find moles, and then convert moles to grams using the molecular mass. This systematic approach ensures accurate results while adhering to significant figure rules.