Understanding Negative Deviation in Chloroform-Acetone Mixtures
Negative deviation from Raoult's law occurs when the vapor pressure of a solution is consistently lower than predicted by Raoult's law for an ideal solution. This phenomenon indicates that the intermolecular attractive forces between the solute and solvent molecules in the mixture are stronger than the forces between molecules of the pure components.
Analyzing Interactions in Chloroform-Acetone Mixtures
To understand the negative deviation in a mixture of chloroform (CHCl3) and acetone (CH3COCH3), consider the intermolecular forces:
- In pure components, molecules interact via dipole-dipole forces and van der Waals forces.
- When chloroform and acetone are mixed, a new type of interaction occurs: hydrogen bonding. The hydrogen atom in chloroform, bonded to chlorine, becomes partially positive. This hydrogen can form a hydrogen bond with the partially negative oxygen atom of the carbonyl group (C=O) in acetone.
- This specific formation of hydrogen bonding between CHCl3 and CH3COCH3 molecules creates stronger attractions between the unlike molecules compared to the attractions between like molecules (CHCl3-CHCl3 or CH3COCH3-CH3COCH3).
- Because the intermolecular forces in the mixture are stronger, molecules have a reduced tendency to escape from the liquid phase into the vapor phase.
- This leads to a lower vapor pressure than theoretically predicted by Raoult's law, resulting in negative deviation.
The key factor driving this negative deviation is the stabilization of the mixture through the formation of hydrogen bonds between chloroform and acetone.
Similar Questions
Match List I with List II :
List I (Quantum Numbers )
$n$, $l$
List II (Orbital) A. 2, 1 I. 3d B. 4, 0 II. 2p C. 5, 3 III. 4s D. 3, 2 IV. 5f Choose the correct answer from the options given below :
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(Given : Molar mass of Cu = $63 \text{ g mol}^{-1}$, $1 \text{ F} = 96487 \text{ C mol}^{-1}$) - Given below is an expression for the rate constant of a first order reaction occurring at a certain temperature, T (K).
$\ln k = 14.34 - \frac{1.25 \times 10^4}{T}$
The energy of activation in $\text{kcal mol}^{-1}$ for the reaction is :
(Given : $k \text{ in s}^{-1}$, $R = 1.987 \text{ cal mol}^{-1} \text{ K}^{-1}$) - The number of hydrogen atoms present in $5.4 \text{ g}$ of urea is :
(Given : Molar mass of urea : $60 \text{ g mol}^{-1}$, $N_A : 6.022 \times 10^{23} \text{ particles mol}^{-1}$) For a certain reaction R $\rightarrow$ Product, the plot of [R] vs time has a negative slope as shown. The order of reaction is :
- Match List I with List II :
List I (Order of reaction) List II (Unit of rate constant) A. Zero order I. $mol^{-1} L s^{-1}$ B. First order II. $mol^{-2} L^2 s^{-1}$ C. Second order III. $s^{-1}$ D. Third order IV. $mol L^{-1} s^{-1}$
Choose the correct answer from the options given below : Calculate emf of the half cell given below :
$$Pt(s) | H_2 (g, 2 \text{ atm}) | HCl (aq, 0.02 \text{ M})$$
$$E_{H_2 /H^+}^\circ = 0 \text{ V}$$
(Given : $\frac{2.303 RT}{F} = 0.059$, $\log 2 = 0.3010$)At 298 K, a certain buffer solution contains equal concentrations of $X^{-}$ and $HX$. $K_b$ for $X^-$ is $10^{-10}$. What is the pH of this buffer solution ?
- Identify the correct statements :
A. The molality of a 2.5 g of ethanoic acid (Molar mass : $60 \text{ g mol}^{-1}$) in 75 g of benzene solution is $0.556 \text{ m}$.
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C. Aquatic species are more comfortable in cold water.
D. The solubility of gas increases with decrease in pressure.
E. For a binary mixture of A and B, the number of moles of A and B are $n_A$ and $n_B$ respectively, the mole fraction of B will be $x_B = \frac{n_A}{n_A + n_B}$.
Choose the correct answer from the options given below : - At a certain temperature T (K), during a process, 500 J is absorbed by the system and work of 200 J is done by the system. Then change in internal energy of the system is :
Important Questions from Physical Chemistry
$CaCO_3(s) + 2HCl(aq) \rightarrow CaCl_2(aq) + CO_2(g) + H_2O(l)$
Consider the above reaction, what mass of $CaCl_2$ will be formed if 250 mL of 0.76 M HCl reacts with 1000 g of $CaCO_3$ ?
(Given: Molar mass of Ca, C, O, H and Cl are 40, 12, 16, 1 and 35.5 g $mol^{-1}$, respectively)- According to Bohr's model of hydrogen atom, which of the following statement is incorrect?
Two vessels A and B are connected via stopcock. The vessel A is filled with a gas at a certain pressure. The entire assembly is immersed in water and is allowed to come to thermal equilibrium with water. After opening the stopcock the gas from vessel A expands into vessel B and no change in temperature is observed in the thermometer. Which of the following statement is true ?Which of the following graphs correctly represents the plot of $K_H$ at 1 bar for gases in water versus temperature?
If equal volumes of $AB_2$ and $XY$ (both are salts) aqueous solutions are mixed, which of the following combination will give a precipitate of $AY_2$ at 300 K ?
(Given $K_{sp}$ (at 300 K) for $AY_2=5.2 \times 10^{-7}$)
