Answers
Answer:
Explanation:
1). Molality is moles of the solute per kilogram of the solvent..........
Molarity is moles of the solute per liter of the solution............
Molalities are more convenient in experiments involving temperature changes...........
2). The normality of a solution is the concentration expressed as the number of equivalent weights (equivalents) of solute per liter of solution. A 1 normal (1 N) solution contains 1 equivalent weight of solute per liter of solution.
The equivalent weights of solute per liter of solution is 2 since in i mole of sulfuric acid there are 2 moles of hydronium ions. To prepare 5N solution of H2SO4 we need 2.5 moles of H2SO4 for every 1 liter of the solution.
A one molar solution has a mass of (H = 2 g; S = 32 g; O = 64 g) 98 grams. A 2.5 molar solution we need 98 g times 2.5 = 245 grams of H2SO4.
To prepare 5N H2SO4 245 grams of the pure acid is needed. The density of this pure acid is 1.84 grams per mL.
3). At room temperature, calcium carbonate has a solubility of 13 ppm , i.e. 13 milligrams per litre of water solvent. The quoted solubility of calcium carbonate is THUS ERRONEOUS, and should not have been proferred as a question at ANY level of chemistry. Please point this out to your instructor, and tell him or her to get his act together. There are MANY soluble salts that could have been chosen…and if you are going to teach chemistry
4). Let the mass of solution is 100g
then, mass of water = 25g
mass of ethanol = 25g
mass of acetic acid = 50g
Now, find number of moles of each components ,
Number of mole of water = mass of water/Molar mass of water
= 25g/18g/mol [ ∵ molar mass of water = 18g/mol ]
≈ 1.4
Number of moles of ethanol = mass of ethanol/molar mass of ethanol
= 25g/46g/mol [ ∵ molar mass of ethanol (C2H5OH) = 46g/mol
= 0.54
Number of moles of acetic acid = mass of acetic acid/molar mass of acetic acid
= 50g/60g/mol [∵ molar mass of acetic acid (CH3COOH) = 60g/mol]
= 0.8
∴ total number of moles = 1.4 + 0.54 + 0.8 = 2.74
Now, mole fraction of water = moles of water/total moles
= 1.4/2.74 =0.51
similarly , mole fraction of ethanol = 0.54/2.74 = 0.197
mole fraction of acetic acid = 0.8/2.74 = 0.291