Question

Find M of 49% W/V H3PO4

Answer 1

Answer:

We are given a solution of H3PO4 having 4.9% of H3PO4 by mass .

Therefore ,

100 g of the solution contains = 4.9 g H3PO4

We know the equation for density of a substance is the mass of the substance divided by the volume of the substance

Density (ρ) = mass(m)/volume(V)

Therefore ,

V = m/ρ

Therefore , volume of H3PO4 = (4.9/1.22) mL

Volume of H3PO4 = 4.01 mL ~ 4 mL

Also ,

100 g of the solution contains = (100 - 4.9) g water

100 g of the solution contains = 95.1 g water .

We know the density of water is 1 g/mL

So , Volume of water = (95.1/1) mL

Volume of water = 95.1 mL

Therefore , the total volume of the solution is = (95.1 + 4)mL

Volume of the solution = 99.1 mL

Therefore ,

99.1 mL of the solution contains = 4.9 g H3PO4

1 mL of the solution contains = (4.9/99.1)g H3PO4

1000 mL of the solution contains = {(4.9 * 1000)/99.1} g H3PO4

1000 mL of the solution contains = 49.434 g H3PO4

Now ,

The molecular mass of phosphoric acid (H3PO4) is = {(1*3) + (31) + (16*4)}

Molecular mass = {3 + 31 + 64}

Molecular mass = 98 g

Therefore the number of moles of phosphoric acid present in 1000 mL of the solution is = (49.434/98) moles

Number of moles = 0.504 moles ~ 0.5 moles

Therefore the solution is 0.5 Molar(M) because molarity is defined as the number of moles of solute present in 1000 mL of the solution .

Answer 2

"It seems this is what you are looking for"

What is the molarity of 4.9% H₃PO₄ solution by mass (density of H₃PO₄ = 1.22g/ml)?

Answer:

The molarity of 4.9% H₃PO₄ solution is equal to 0.61M.  

Explanation:

In the given data,

4.9% H₃PO₄ solution by mass means 4.9g of H₃PO₄ is added in 100g of solution.

Density of H₃PO₄ solution = 1.22g/ml

Volume of H₃PO₄ solution =  $\frac{mass}{density}=\frac{100}{1.22}$

                                       $= 81.96ml = 0.08196 L$

As we know the molecular weight of  H₃PO₄ = 98g

Number of moles of  H₃PO₄ $=\frac{4.9}{98} =0.05moles$

Molarity of solution = moles of solute/volume(L)

Molarity of  H₃PO₄ solution  $=\frac{0.05}{0.08196}=0.61molL^{-1}=0.61M$

Therefore the molarity of given solution is 0.61M.