What is the mass of dry NaCl sample should be taken for 100 cm3 of 0.5 mol/dm3 aqueous solution?
To determine the mass of a dry NaCl sample needed for a given volume and concentration of an aqueous solution, you need to use the equation:
Concentration (mol/dm³) = Moles of solute / Volume of solution (dm³)
In this case, you have a concentration of 0.5 mol/dm³ and a volume of 100 cm³ (which is equal to 0.1 dm³). Let's calculate the moles of NaCl needed:
Moles of NaCl = Concentration × Volume
Moles of NaCl = 0.5 mol/dm³ × 0.1 dm³
Moles of NaCl = 0.05 moles
Now, to determine the mass of the NaCl sample, you need to use the equation:
Mass = Moles × Molar mass
The molar mass of NaCl is 58.44 g/mol. Let's calculate the mass:
Mass = 0.05 moles × 58.44 g/mol
Mass = 2.922 g
Therefore, a dry NaCl sample with a mass of approximately 2.922 grams should be taken for 100 cm³ of a 0.5 mol/dm³ aqueous solution.