UA Session Question

[Nina Fukui 2J]

Hi! Could someone teach me how to do part b of this question?

Arsenic is a toxic substance that can sometimes be found in groundwater. Arsenic has a molar
mass of 74.922 g/mol.

a) Calculate the molarity if 1.125 grams of arsenic are added to 235 mL of water.

b) What volume (mL) of concentrated arsenic solution from part A would need to be diluted
in order to obtain 235 mL of solution at a concentration of 5.60x10-7
M?

[Isabel_Eslabon_2G]

Hello.

For part B you need to use the molarity from part A & use this formula:



M1=Molarity from Part A
V1= You are solving for this.
M2=5.60*10^-7
V2=0.235L

I did the conversion, but this formula needs to be in liters, so once you find the value of V1, convert back to mL.

[ShinwooKim_3E]

Hi! Could someone teach me how to do part b of this question?

Arsenic is a toxic substance that can sometimes be found in groundwater. Arsenic has a molar
mass of 74.922 g/mol.

a) Calculate the molarity if 1.125 grams of arsenic are added to 235 mL of water.

b) What volume (mL) of concentrated arsenic solution from part A would need to be diluted
in order to obtain 235 mL of solution at a concentration of 5.60x10-7
M?

You use the equation M1V1= M2V2, and always convert mL to L and any masses to grams (remember for other topics these units of measurement are not the same).