Advertisements
Advertisements
Question
Calculate (a) molality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL−1.
Advertisements
Solution
Given: Let mass of solution in water = 100 g, then mass of KI = 20 g
∴ Mass of solvent (water) = 100 − 20 = 80 g = 0.080 kg
(a) Molar mass of KI = 39 + 127 = 166 g mol−1
∴ Moles of KI = `(20 "g")/(166 "g mol"^(-1))`
= 0.120 mol
Molality of solution = `"Number of moles of KI"/"Mass of solvent in kg"`
= `(0.120 "mol")/(0.080 "kg")`
= 1.5 mol kg−1
(b) Density of the solution = 1.202 g mL−1
∴ Volume of solution = `"Mass"/"Density"`
= `(100 "g")/(1.202 "g mL"^(-1))`
= 83.2 mL
= 0.0832 L
Molarity of the solution = `"Number of moles of solute"/"Volume of solution in L"`
= `(0.120 "mol")/(0.0832 "L")`
= 1.44 M
(c) No. of moles of KI = 0.120 mol
No. of moles of water = `"Mass of water"/"Molar mass of water"`
= `(80 "g")/(18 "g mol"^(-1))`
= 4.44 mol
Mole fraction of KI = `"Number of moles of KI"/"Total number of moles in solution"`
= `0.12/(0.120 + 4.44)`
= `0.120/4.560`
= 0.0263
APPEARS IN
RELATED QUESTIONS
A solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass. Calculate the mass percentage of the resulting solution.
An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H6O2) and 200 g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g mL−1, then what shall be the molarity of the solution?
When KOH solution is added to potassium dichromate solution the colour of solution
changes to yellow, because _______
(A) chromate ion changes to dichromate ion
(B) dichromate ion changes to chromate ion
(C) oxidation number of chromium changes from + 6 to + 4
(D) oxidation number of chromium changes from + 4 to +6
A sample of 12 M Concentrated hydrochloric acid has a density 1.2 M gL-1 calculate the molality.
When a solute is present in trace quantities the following expression is used:
Molarity of liquid HCl will be if the density of the solution is 1.17 gm/cc.
1 M, 2.5 litre NaOH solution is mixed with another 0.5 M, 3 litre NaOH solution. Then find out the molarity of the resultant solution:
10 g of NaCl is dissolved in 106 g of the solution. Its concentration is ____________.
25 ml of a solution of barium hydroxide on titration with a 0.1 molar solution of hydrochloric acid gave a titre value of 35 ml. The molarity of barium hydroxide solution was ______.
200 ml of water is added to 500 ml of 0.2 M solution. What is the molarity of this diluted solution?
Out of molality (m), molarity (M), formality (F) and mole fraction (x), those which are independent of temperature are:
The number of moles of NaCl in 3 litres of 3 M solution is ____________.
Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?
(iii) w/V (mass by volume percentage)
Carbon percentage (by weight) in crude petroleum may be about
The number of electrons involved in the reduction of one nitrate ion to hydrazine is
Calculate the mass percent of benzene (CoH6) and carbon tetrachloride (ccl4) if 22 g of benzene is dissolved in 122 g of carbon tetrachloride.
