Calculate the mass of salt needed to prepare 100 cm3
of 0.05 M solution of:
(i) Fe(NH4)2(SO4)2.6H2O (ii) FeNH4(SO4)2.12H2O
1) 45g
2) 30g
To calculate the mass of salt needed to prepare 100 cm^3 of a 0.05 M solution, we need to determine the molar mass of the compound and use the formula:
Mass of salt (g) = molar mass (g/mol) * volume (L) * molarity (mol/L)
Let's calculate the mass of salt needed for each compound:
(i) Fe(NH4)2(SO4)2·6H2O:
Molar mass of Fe(NH4)2(SO4)2·6H2O = (55.845 g/mol) + 2(18.039 g/mol) + 2(32.06 g/mol) + 4(16.00 g/mol) + 6(18.015 g/mol)
= 392.14 g/mol
Volume in liters = 100 cm^3 = 100/1000 = 0.1 L
Mass of salt (i) = 392.14 g/mol * 0.1 L * 0.05 mol/L
= 1.9607 g or approximately 1.96 g
(ii) FeNH4(SO4)2·12H2O:
Molar mass of FeNH4(SO4)2·12H2O = (55.845 g/mol) + (18.039 g/mol) + 2(32.06 g/mol) + 8(16.00 g/mol) + 12(18.015 g/mol)
= 568.35 g/mol
Volume in liters = 100 cm^3 = 100/1000 = 0.1 L
Mass of salt (ii) = 568.35 g/mol * 0.1 L * 0.05 mol/L
= 2.8417 g or approximately 2.84 g
Therefore, the mass of salt needed to prepare 100 cm^3 of a 0.05 M solution is approximately 1.96 g for Fe(NH4)2(SO4)2·6H2O and 2.84 g for FeNH4(SO4)2·12H2O.
To calculate the mass of salt needed to prepare a solution, you need to know the molar mass of the salt and the volume and concentration of the solution.
(i) Fe(NH4)2(SO4)2.6H2O:
1. Determine the molar mass of the compound by adding the atomic masses of each element in the formula.
Fe(NH4)2(SO4)2.6H2O:
Fe: 55.845 g/mol
N: 14.007 g/mol
H: 1.008 g/mol
S: 32.06 g/mol
O: 16.00 g/mol
Calculate the total molar mass:
(55.845 g/mol) + 2(14.007 g/mol) + 2(32.06 g/mol) + 6[(1.008 g/mol) + 2(16.00 g/mol)]
2. Multiply the molar mass by the volume and concentration of the solution to get the mass needed.
Given:
Volume of solution = 100 cm3
Concentration (Molarity) = 0.05 M
To convert the volume from cm3 to liters, divide by 1000:
Volume of solution = 100 cm3 / 1000 = 0.1 L
Mass = Volume x Concentration x Molar mass
Mass = 0.1 L x 0.05 M x Molar mass of Fe(NH4)2(SO4)2.6H2O
Substitute the molar mass value and calculate the mass.
(ii) FeNH4(SO4)2.12H2O:
Follow the same steps as above, but use the molar mass of FeNH4(SO4)2.12H2O instead in step 1.
FeNH4(SO4)2.12H2O:
Fe: 55.845 g/mol
N: 14.007 g/mol
H: 1.008 g/mol
S: 32.06 g/mol
O: 16.00 g/mol
Calculate the total molar mass:
(55.845 g/mol) + (14.007 g/mol) + 2(32.06 g/mol) + 12[(1.008 g/mol) + 2(16.00 g/mol)]
Then, substitute the calculated molar mass into step 2 and calculate the mass needed.
1) 45g
2) 30g