The solution contains 39.4% of LiF. Assume that the solution is 100ml. The molar mass of LiF is 25.939, the amount of LiF in mole would be: 100ml * 1g/ml * 39.4%/ 25.939g/mol= 1.52 mol LiF
Then the mass of the water would be: 100gram- 39.4g= 60.6g
If the molar mass of water is 18.015 the mole of the water would be: 60.6g/ 18.015g/mol= 3.36 mol
.
The mole fraction would be:1.52 mol/ 1.52+3.36= 0.339
Answer is B because C and D make has nothing to do with the question and A isn’t it
Answer:
0.940mol &
0.000301mol respectively.
Explanation:
number of moles = given mass / molar mass
given mass of Nacl = 55g Molar mass = 23 + 35.5
n=m/M = 55g/58.5g/mol = 0.940mol
note- (add the atomic weights of sodium and chlorine to get the molar mass of Nacl.) = 58.5g/mol
similarly, NaCO3 = 23 + 12 + 16*3 = 83g/mol
n=m/M = 0.025g/83g/mol = 3.01 * 10^-4 = 0.000301mol
extra: If you ever get asked to put it in number of particles just use the relation of 1mole = 6.02 * 10^23 particles.
Step 1: write the equation:
P₄(s) + 6F₂(g) → 4PF₃(g)
Step 2: Molar mass of P₄ = 30.97 g/mol × 4 = 123.88 g/mol
Step 3: Number of moles of phosphorus
n = m/M
n = 8.5 g/123.88g/mol
n = 0.07 moles
Step 4: 0.07 × 12 = 0.84 moles of fluorine.
Fluorine is diatomic gas so we multiplied the number of moles by 12.
Step 5: To find the mass of fluorine we multiply the number of moles with the molar mass.
Mass of fluorine = 0.84 × 228
= 191.52 grams.
