Advertisements
Advertisements
प्रश्न
Derive the relationship between the degree of dissociation of an electrolyte and van’t Hoff factor.
A substance dissociates in solution to give n ions. Derive an expression for degree of dissociation in terms of van’t Hoff factor i and n.
Advertisements
उत्तर
The weak electrolytes involve the concept of degree of dissociation (α) that changes the van’t Hoff factor.
Consider an electrolyte AxBy that dissociates in aqueous solution as
| \[\ce{A_xB_y \phantom{...}<=> \phantom{..} xA^{y+} + \phantom{..} yB^{x−}}\] | |
| Initially | 1 mol 0 0 |
| At equilibrium | (1 − α) mol (xα mol) (yα mol) |
If α is the degree of dissociation of the electrolyte, then the moles of cations are xα and those of anions are yα equilibrium. We have dissolved just 1 mol of electrolyte initially. α mol of electrolyte dissociates, and (1 – α) mol remains undissociated at equilibrium.
Total moles after dissociation = (1 – α) + (xα) + (yα)
= 1 + α (x + y − 1)
= 1 + α (n − 1)
Where, n = x + y = moles of ions obtained from the dissociation of 1 mole of electrolyte.
The van’t Hoff factor given as
i = `"actual moles of particles insolution after dissociation"/"moles of formula units dissolved in solution"`
= `(1 + alpha (n - 1))/1`
Hence, i = 1 + α(n − 1) or α = `(i - 1)/(n - 1)`
संबंधित प्रश्न
A 0.1 m solution of K2SO4 in water has a freezing point of –4.3°C. What is the value of van’t Hoff factor if Kf for water is 1.86 K kg mol–1?
Answer the following in one or two sentences.
What is van’t Hoff factor?
Answer the following in one or two sentences.
How is van’t Hoff factor related to degree of ionization?
Answer the following in one or two sentences.
Which of the following solution will have higher freezing point depression and why?
i. 0.1 m NaCl
ii. 0.05 m Al2(SO4)3
A 0.15 m aqueous solution of KCl freezes at - 0.510 °C. Calculate i and osmotic pressure at 0 °C. Assume the volume of solution equal to that of water.
If the van't Hoff-factor for 0.1 M Ba(NO3)2 solution is 2.74, the degree of dissociation is ______.
Relationship between van't Hoff's factor (i) and degree of dissociation (α) is ______.
The osmotic pressure of a solution containing 10 g of cane sugar dissolved in 100 mL of water at 70°C is ____________.
If van't Hoff factor of monofluoroacetic acid in water is 1.076. What is it's degree of dissociation?
Which of the following salts of same concentration will have same value of van't Hoff factor as that of K4[Fe(CN)6]?
Van't Hoff factor for K3[Fe(CN)6] is 3.333. What is it's percentage dissociation in water?
Why is observed molar mass of acetic acid in benzene is greater than actual molar mass?
Which of following 0.1 m aqueous solution exhibits highest osmotic pressure at 25°C?
Solution of 'A' containing 1.73 g of it in 100 cm3 of water is found to be isotonic with a 3.42% (w/v) solution of sucrose. The molecular weight of A is ______. (At. mass C = 12, H = 1, 0 = 16)
Van't Hoff factor (i) for centimolal solution of \[\ce{K3[Fe(CN)6]}\] is 3.333. What is its percentage dissociation?
0.01 m aqueous formic acid solution freezes at – 0.021°C. Calculate its degree of dissociation, Kf = 1.86 K kg mol–1.
The equation that represent general van't Hoff equation is ______.
For which among the following equimolar aqueous solutions Van't Hoff factor has the lowest value?
Write modification of expressions of colligative properties with the help of van't Hoff factor.
The value of van't Hoff factor will be minimum for ______.
The depression in freezing point of 0.2 m aqueous solution of an electrolyte is 0.7 K. Calculate its percent degree of dissociation. [Kf for water = 1.86 K kg mol-1; n = 2]
