one litre of a sample hard water contain 4.44mg cacl2 and 1.9mg of mgcl2. What is the total hardness in terms ppm of cac03?
http://en.wikipedia.org/wiki/Hard_water
To calculate the total hardness of the water sample in terms of ppm (parts per million) of CaCO3, we need to convert the concentrations of CaCl2 and MgCl2 into their respective concentrations of CaCO3.
First, let's calculate the concentration of CaCO3 from CaCl2:
1 mole of CaCl2 is equivalent to 1 mole of CaCO3. The molar mass of CaCl2 is 110.98 g/mol, and the molar mass of CaCO3 is 100.09 g/mol (one calcium atom, one carbon atom, and three oxygen atoms).
To convert the mass of CaCl2 to moles, divide it by the molar mass:
4.44 mg / 110.98 g/mol = 0.0399 mmol of CaCl2
Since 1 mole of CaCl2 is equivalent to 1 mole of CaCO3, the concentration of CaCO3 is also 0.0399 mmol.
To convert this to ppm, we need to consider the volume of the sample. Since we have 1 litre (1000 ml) of sample, the concentration of CaCO3 in ppm can be calculated as follows:
ppm = (Concentration of CaCO3 in mmol) × (Molar mass of CaCO3 in g/mol) / (Volume of sample in ml)
ppm = (0.0399 mmol) × (100.09 g/mol) / 1000 ml = 3.99 ppm
Similarly, let's calculate the concentration of CaCO3 from MgCl2:
1 mole of MgCl2 is equivalent to 1 mole of MgCO3. The molar mass of MgCl2 is 95.21 g/mol, and the molar mass of MgCO3 is 84.31 g/mol.
To convert the mass of MgCl2 to moles, divide it by the molar mass:
1.9 mg / 95.21 g/mol = 0.0199 mmol of MgCl2
Since 1 mole of MgCl2 is equivalent to 1 mole of MgCO3, the concentration of MgCO3 is also 0.0199 mmol.
To convert this to ppm, considering the same volume of the sample:
ppm = (Concentration of MgCO3 in mmol) × (Molar mass of MgCO3 in g/mol) / (Volume of sample in ml)
ppm = (0.0199 mmol) × (84.31 g/mol) / 1000 ml = 1.67 ppm
Finally, to get the total hardness in ppm of CaCO3, we add the concentrations of CaCO3 from CaCl2 and MgCl2:
Total hardness = concentration of CaCO3 from CaCl2 + concentration of CaCO3 from MgCl2
Total hardness = 3.99 ppm + 1.67 ppm = 5.66 ppm
Therefore, the total hardness of the water sample in terms of ppm of CaCO3 is 5.66 ppm.