Advertisements
Advertisements
Question
Define van’t Hoff factor.
Solution
The van’t Hoff factor is defined as the ratio of observed colligative property produced by a given concentration of electrolyte solution to the property observed for the same concentration of non-electrolyte solution.
Van't Hoff factor :
To account for the extent of dissociation or association, van’t Hoff introduced a factor i , known as the van’t Hoff factor.
`i = "Observed colligative property of electrolyte solution"/"Observed colligative property of non-electrolyte solution of same concentration"`
It is related to the degree of dissociation as,
`a = "i - 1"/"n’ - 1"`
Value of i :
For association, i < 1
For dissociation, i > 1
No association or dissociation, i = 1
RELATED QUESTIONS
Derive van’t Hoff general solution equation
3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).
(Given : Molar mass of benzoic acid = 122 g mol−1, Kf for benzene = 4.9 K kg mol−1)
Calculate the amount of benzoic acid (C6H5COOH) required for preparing 250 mL of 0.15 M solution in methanol.
19.5 g of CH2FCOOH is dissolved in 500 g of water. The depression in the freezing point of water observed is 1.0°C. Calculate the van’t Hoff factor and dissociation constant of fluoroacetic acid.
How van’t Hoff factor is related to the degree of dissociation?
How will you convert the following in not more than two steps:
Benzoic acid to Benzaldehyde
How will you convert the following in not more than two steps:
Acetophenone to Benzoic acid
Give reasons for the following
Elevation of the boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.
Predict whether van’t Hoff factor, (i) is less than one or greater than one in the following:
CH3COOH dissolved in water
The Van't Hoff factor (i) for a dilute aqueous solution of the strong elecrolyte barium hydroxide is (NEET) ______.
The freezing point depression constant for water is 1.86° K Kg mol-1. If 5 g Na2SO4 is dissolved in 45 g water, the depression in freezing point is 3.64°C. The Vant Hoff factor for Na2SO4 is ______.
Phenol dimerizes in benzene having van’t Hoff factor 0.54. What is the degree of association?
We have three aqueous solutions of NaCl labelled as ‘A’, ‘B’ and ‘C’ with concentrations 0.1 M, 0.01 M and 0.001 M, respectively. The value of van’t Hoff factor for these solutions will be in the order ______.
The values of Van’t Hoff factors for KCl, NaCl and K2SO4, respectively, are ______.
Van't Hoff factor I is given by expression.
Maximum lowering of vapour pressure is observed in the case of ______.
When 9.45 g of ClCH2COOH is added to 500 mL of water, its freezing point drops by 0.5°C. The dissociation constant of ClCH2COOH is x × 10−3. The value of x is ______. (Rounded-off to the nearest integer)
[\[\ce{K_{f(H_2O)}}\] = 1.86 K kg mol−1]
A storage battery contains a solution of H2SO4 38% by weight. At this concentration, Van't Hoff Factor is 2.50. At the battery content freeze temperature will be ______ K.
(Kf = 1.86 K Kg mol−1)
The degree of dissociation of Ca(NO3)2 in a dilute aqueous solution containing 7 g of the salt per 100 g of water at 100°C is 70%. If the vapour pressure of water at 100°C is 760 mm. The vapour pressure of the solution is ______ mm.
Consider the reaction
\[\begin{bmatrix}\begin{array}{cc}
\phantom{.......}\ce{CH3}\\
\phantom{....}|\\
\ce{CH3CH2CH2 - \overset{⊕}{N} - CH2CH3}\\
\phantom{....}|\\
\phantom{.......}\ce{CH3}
\end{array}\end{bmatrix}\]\[\ce{OH^- ->[Heat] ?}\]
Which of the following is formed in a major amount?
A molecule M associates in a given solvent according to the equation \[\ce{M <=> (M)_n}\]. For a certain concentration of M, the van't Hoff factor was found to be 0.9 and the fraction of associated molecules was 0.2. The value of n is ______.
When 19.5 g of F – CH2 – COOH (Molar mass = 78 g mol−1), is dissolved in 500 g of water, the depression in freezing point is observed to be 1°C. Calculate the degree of dissociation of F – CH2 – COOH.
[Given: Kf for water = 1.86 K kg mol−1]
Why is the value of van't Hoff factor for ethanoic acid in benzene close to 0.5?
Why is boiling point of 1 M NaCl solution more than that of 1 M glucose solution?
