# To prepare a red dye stock solution, a student carefully measures out 0.0453 g of red dye #3 onto a weigh paper, records the mass then carefully transfers the red solid to a 100.0 mL volumetric flask. To make sure the transfer is quantitative, the student uses a distilled water squirt bottle to rinse the residue on the weigh paper directly into the volumetric flask. The student then carefully fills the volumetric flask to the line with distilled water. What is the concentration of this stock solution?

We need to calculate the concentration of the stock solution in terms of molarity.

Molarity: The molarity of a substance can be defined as a mole of solute per volume of solution in Litre. The formula of molarity is:

`Molarity = ( Mol e of solute (mol)) / (volume of solution (L))`

The unit of molarity is `mol L^-1` or "M"

Given:

Mass of red dye #3 = 0.0453 g

Volume of solution = 100.0 mL

Step 1: To convert the mass of dye to mole using the molar mass of red dye #3 as:

Molar mass of red dye #3 = 879.86 `g/(mol)`

Mole of red dye #3 = `0.0453 g xx (1mol)/(879.86g) = 5.15xx10^(-5)mol `

Step 2: To convert the volume of solution from mL to L using conversion factor 1 L = 1000mL as:

Volume of Solution = `100.0mL xx (1L)/(1000mL) = 0.1 L`

Step 3: Plugging the values of mole and volume in formula of molarity as:

Molarity = `(5.15 xx 10^(-5)mol)/(0.1L)= 5.15 xx 10^(-4) (mol)/(L)`

Hence, the concentration of stock solution is `5.15 xx 10^(-4) (mol)/(L)`