4 gm of N aOH are present in 0.1dm3
solution have specific gravity 1.038 gm/ml. calculate:
a. Molality of N aOH solution;
b. Molarity of N aOH solution.
Molarity=moles/literssolution
= (4/40)/.1
Molality=moles/kgsolution
= (4/40)/(density*volume)
= (4/40)/(1.038g/ml*100ml)
Molarity=moles/literssolution
= (4/40)/.1
Molality
= You have to know the volume of solvent. so start with the density of the solution and mass.
massolution=density*volume=1.038g/ml*100ml=103.8 grams
but you know you added 4g of NaOH, so the mass of the solvent must have been 99.2grams
Molality=molessolute/kgsolvent
= (4/40)/(.0992)
To calculate the molality and molarity of the NaOH solution, we'll need to use the given information about the mass of NaOH and the volume of the solution.
a. Molality (m):
Molality is defined as the number of moles of solute (NaOH) per kilogram of solvent (water). To calculate the molality, we need the mass of NaOH and the mass of water in the solution.
1. Calculate the mass of water:
Given that the solution has a specific gravity of 1.038 g/ml, we can find the mass of water in the solution.
Mass of water = Volume of solution x Specific gravity
= 0.1 dm^3 x 1.038 g/ml
= 0.1038 kg
2. Calculate the moles of NaOH:
Number of moles = Mass of NaOH / Molar mass of NaOH
Molar mass of NaOH = (1 x 23) + (1 x 16) + (1 x 1)
= 23 + 16 + 1
= 40 g/mol
Number of moles of NaOH = 4 g / 40 g/mol
= 0.1 mol
3. Calculate molality:
Molality (m) = Moles of solute / Mass of solvent (in kg)
= 0.1 mol / 0.1038 kg
≈ 0.962 mol/kg
Therefore, the molality of the NaOH solution is approximately 0.962 mol/kg.
b. Molarity (M):
Molarity is defined as the number of moles of solute (NaOH) per liter of solution. To calculate the molarity, we just need to know the volume of the solution.
1. Calculate the moles of NaOH (already calculated in part a):
Number of moles = 0.1 mol
2. Calculate molarity:
Molarity (M) = Moles of solute / Volume of solution (in L)
= 0.1 mol / 0.1 L
= 1 mol/L
Therefore, the molarity of the NaOH solution is 1 M.