If you are using 5.25% (mass/mass) bleach solution and you determine that the density of the bleach solution is 1.08 g/mL, how many moles of sodium hypochlorite are present in a 4.00 mL sample?
To determine the number of moles of sodium hypochlorite present in a 4.00 mL sample of the 5.25% bleach solution, we need to perform a series of calculations.
Step 1: Calculate the mass of the bleach solution.
To do this, we multiply the density of the bleach solution (1.08 g/mL) by the volume of the sample (4.00 mL):
Mass of bleach solution = density × volume = 1.08 g/mL × 4.00 mL = 4.32 g
Step 2: Calculate the mass of sodium hypochlorite in the bleach solution.
Since the bleach solution is 5.25% bleach (mass/mass), we can calculate the mass of sodium hypochlorite by multiplying the mass of the bleach solution by the percentage of bleach:
Mass of sodium hypochlorite = mass of bleach solution × percentage of bleach = 4.32 g × (5.25/100) = 0.2268 g
Step 3: Convert mass to moles.
To convert the mass of sodium hypochlorite to moles, we need to use the molar mass of sodium hypochlorite. The molecular formula for sodium hypochlorite (NaClO) consists of one sodium atom (Na), one chlorine atom (Cl), and one oxygen atom (O). The molar masses of these elements are approximately 22.99 g/mol (sodium), 35.45 g/mol (chlorine), and 15.99 g/mol (oxygen), respectively. Therefore, the molar mass of sodium hypochlorite is:
Molar mass of sodium hypochlorite (NaClO) = molar mass of sodium + molar mass of chlorine + molar mass of oxygen
= 22.99 g/mol + 35.45 g/mol + 15.99 g/mol
= 74.43 g/mol
Now we can convert the mass of sodium hypochlorite to moles:
Number of moles = mass / molar mass = 0.2268 g / 74.43 g/mol = 0.003049 mol (rounded to five decimal places)
Therefore, there are approximately 0.003049 moles of sodium hypochlorite present in a 4.00 mL sample of the 5.25% bleach solution.