Taking into account the definition of molarity, molar mass and dilution:
Molar concentration or molarity is a measure of the concentration of a solute in a solution and indicates the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of solute by the volume of the solution:
[tex]molarity=\frac{number of moles}{volume}[/tex]
Molarity is expressed in units [tex]\frac{moles}{L}[/tex].
The molar mass of substance is a property defined as its mass per unit quantity of substance, in other words, molar mass is the amount of mass that a substance contains in one mole.
If the bleach is a 0.70 mol/L solution of sodium hypochlorite and is required to prepare 1.5 L of chlorine bleach, replacing in the definition of molarity you get:
0.70 [tex]\frac{moles}{L}[/tex]=[tex]\frac{number of moles}{1.5 L}[/tex]
Solving:
0.70 [tex]\frac{moles}{L}[/tex]× 1.5 L= number of moles
1.05 moles= number of moles
The molar mass of sodium hypochlorite is 74.44 g/mol. So you can apply the following rule of three: If by definition of molar mass 1 mole of the compound contains 74.44 grams, 1.05 moles of the compound contains how much mass?
[tex]mass=\frac{1..05 molesx74.44 grams}{1 mole}[/tex]
mass= 78.162 grams
Finally, the mass of sodium hypochlorite (NaClO) required is 78.162 grams.
Dilution is the process of reducing the concentration of solute in solution, which is accomplished by simply adding more solvent to the solution at the same amount of solute.
In a dilution the amount of solute does not change, but as more solvent is added, the concentration of the solute decreases, as the volume (and weight) of the solution increases.
A dilution is mathematically expressed as:
Ci×Vi = Cf×Vf
where
In this case, you know:
Replacing in the definition of dilution:
12 mol/L× 420mL= Cf× 2000 mL
Solving:
(12 mol/L× 420mL)÷ 2000 mL= Cf
2.52 mol/L= Cf
In summary, the final concentration of a sodium hydroxide solution is 2.52 mol/L.
Learn more about
molar mass:
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molarity:
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dilution:
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