Question

The Forhans branded toothpaste contains 0.754g of sodium in form of sodium monofluoro ortho phosphate $\left( {N{a_3}P{O_4}F} \right)$ in 100mL solution. Calculate the mass of $\left( {N{a_3}P{O_4}F} \right)$ present in a 100mL solution.
A) 3
B) 2
C) 4
D) 1

Answer 1

To calculate the amount of $\left( {N{a_3}P{O_4}F} \right)$ present in 100 mL of solution, we will find the number of moles of $\left( {N{a_3}P{O_4}F} \right)$ and then by using the below formula we will find out the mass of $\left( {N{a_3}P{O_4}F} \right)$
Mass in g = Number of moles $\times$ Molar mass

Complete step by step answer:
Avogadro number is the number of atoms or molecules present in 1 mol of any substance.
Quantity in grams can be calculated as follows:
Mass in g = Number of moles $\times$ Molar mass
Let us calculate the number of moles and the molecular weight of $\left( {N{a_3}P{O_4}F} \right)$
Molecular weight of $\left( {N{a_3}P{O_4}F} \right)$=183
We know that 1mole of $\left( {N{a_3}P{O_4}F} \right)$= 3 mole $Na$= 1 mole $F$
Therefore, number of mole of $Na$= mass in g/molar mass = 0.754/23 = 0.033
Therefore, from above number of mole of $\left( {N{a_3}P{O_4}F} \right)$= 0.033/3=0.011
Therefore, the total amount of $\left( {N{a_3}P{O_4}F} \right)$ present in 100 mL of solution =
Mass in g = Number of moles $\times$ Molar mass
Mass = 0.11$\times$183 = 2.0 g
Thus, 2.0 g of $\left( {N{a_3}P{O_4}F} \right)$ is present in 100 mL of given solution.

So, the correct answer is Option B.

Additional information:
Sodium MonoFluoroPhosphate which is commonly abbreviated MFP, is an inorganic compound which is a type of salt, commonly used in toothpaste. This MFP is colourless, odourless and is water soluble. It is best known as an ingredient in toothpaste. The Fluoride in this protects the tooth from attack by bacteria that cause dental cavities.

Note: The structure of the fluorophosphate anion contains phosphorus at the centre of a tetrahedron surrounded by three oxygen atoms and one fluorine atom. MFP structure is similar to and is isoelectronic with $N{a_2}S{O_4}$.