Advertisements
Advertisements
Question
A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):
- express this in percent by mass.
- determine the molality of chloroform in the water sample.
Advertisements
Solution
(i) 15 ppm (by mass) means 15 parts per million (106) of the solution.
∴ Percent by mass = `15/10^6 xx 100`
= 1.5 × 10−3
(ii) Molar mass of chloroform (CHCl3) = 1 × 12 + 1 × 1 + 3 × 35.5
= 119.5 g mol−1
Now, according to the question,
15 g of chloroform is present in 106 g of the solution.
i.e., 15 g of chloroform is present in (106 − 15) ≈ 106 g of water.
Number of moles of CHCl3 = `"Mass (in g)"/"Molar mass"`
= `15/119.5`
∴ Molality of the solution = `(15/119.5 "mol")/(10^6) xx 1000`
= 1.25 × 10−4 m
APPEARS IN
RELATED QUESTIONS
Why is molality of a solution independent of temperature?
Calculate the molarity of the following solution:
30 g of Co(NO3)2 . 6H2O in 4.3 L of solution.
Define molarity (M).
Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is 1.504 g mL−1?
If the solubility product of CuS is 6 × 10−16, calculate the maximum molarity of CuS in aqueous solution.
Calculate the mass percentage of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 g of C9H8O4 is dissolved in 450 g of CH3CN.
Which of the following is a quantitative description of the solution?
When a solute is present in trace quantities the following expression is used:
Which of the following units is useful in relating concentration of solution with its vapour pressure?
Mole fraction of C3H5(OH)3 in a solution of 36 g of water and 46 g of glycerine is ______.
Which of the following is a correct statement for C2H5Br?
Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?
M (Molarity)
What is the ratio of mass of an electron to the mass of a proton?
The de Broglie wavelength of a car of mass 1000 kg and velocity 36 km/hr is :
Calculated the mole fraction of benzene in a solution containing 30% by mass of its is carbon tetrachloride
A given solution of H2O2 is 30 volumes. Its concentration in terms of molarity is ______.
A sample of Ferrous sulphide reacts with dil. H2SO4 to from H2S which contains 9% hydrogen by volume. The percentage of fee in the sample, is ______.
4 ml of pure A (d = 2.45 gm/ml) was added to 46 ml of B (d = `25.1/23` gm/ml), the molarity of a solution of A in B will be ______, if the density of the final solution is 1.8 gm/ml.
Given: Molar mass of A = 98, Molar mass of B = 46
Calculate the molarity of the following solution:
30 mL of 0.5 M H2SO4 diluted to 500 mL.
