Tag: various mixtures

Questions Related to various mixtures

If the heat of combustion of carbon monoxide at constant volume and at $17^o$C is $-283.3$ kJ, then its enthalpy of combustion at constant pressure($R=8.314J degree^{-1} mol^{-}$)

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. $-284.5$ kJ

  2. $284.5$ kJ

  3. $384.5$ kJ

  4. $-384.5$ kJ

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Correct Option: A
Explanation:
Solution:- (A) $- 284.5 \; kJ$
Heat change at constant volume for the combustion of carbon monoxide $= -283.3 \; kJ$
${CO} _{\left( g \right)} + \cfrac{1}{2} {{O} _{2}} _{\left( g \right)} \longrightarrow {C{O} _{2}} _{\left( g \right)}$
From the above reaction,
$\Delta{{n} _{g}} = {n} _{P} - {n} _{R} = 1 - \left( \cfrac{1}{2} + 1 \right) = - \cfrac{1}{2}$
Temperature $\left( T \right) = 17 ℃ = \left( 17 + 273 \right) K = 290 K \; \left( \text{Given} \right)$
Now from first law of thermodynamics,
$\Delta{H} = \Delta{E} + \Delta{{n} _{g}} RT$
$\Delta{H} = -283.3 + \left( -\cfrac{1}{2} \right) \times 8.314 \times {10}^{-3} \times 290$
$\Rightarrow \Delta{H} = -283.3 - 1.205 = - 284.505 \; kJ$
Hence the heat of reaction at constant pressure will be $- 284.5 \; kJ$.

Dissolution of ionic solid in water is possible when:

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. $H$ lattice $> H$ hydration

  2. $H$ lattice $= H$ hydration

  3. $H$ hydration $: H$ lattice = 2:1

  4. $H$ hydration $> H$ lattice

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Correct Option: D
Explanation:

Solution:- (D) ${H} _{\text{hydration}} > {H} _{\text{lattice}}$

In order to dissolve an ionic solid, water molecules must break up the interactions between all of the ions in the solid. The heat of hydration $\left( {H} _{\text{hydration}} \right)$ offsets the lattice energy $\left( {H} _{\text{lattice}} \right)$ of an ionic solid to allow for solution formation to occur typically when ${H} _{\text{hydration}} > {H} _{\text{lattice}}$.

For an ideal binary liquid solution with $P^{\circ} _{A} > P^{\circ} _{B}$, which relation between $X _{A}$ (mole fraction of A in liquid phase) and $Y _{A}$(mole fraction of $A$ in vapour phase) is correct?

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. $Y _{A} < Y _{B}$

  2. $X _{A} > X _{B}$

  3. $\dfrac{Y _{A}}{Y _{B}} > \dfrac{X _{A}}{X _{B}}$

  4. $\dfrac{Y _{A}}{Y _{B}} < \dfrac{X _{A}}{X _{B}}$

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Correct Option: A
Explanation:

For an ideal binary liquid solution with $P _\overset {o}{A}>P _\overset {o}{B}$.

We know that, from Henry's law
$P _\overset {o}{A}\propto X _A$
So, $X _A > X _B$.
If mole fraction of $A$ in liquid phase is more then mole fraction of $A$ in vapour phase is less so, $Y _A < Y _B$.

Which of the following are correct about Tyndall effect?

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. True solution do not show Tyndall effect due to very small size of the particles

  2. The diameter of the particles of the dispersed phase must not be much smaller than the wavelength of light used

  3. Tyndall effect is very weak in case of lyophobic sols

  4. The refractive index of the dispersed phase and dispersion must differ considerably

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Correct Option: A

$100\ ml$ of an aqueous solution contains $6.0\times {10}^{21}$ solute molecules. The solution is diluted to $1$ lit. The number of solute molecules present in $10\ ml$ of the dilute solution is:

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. $6.0\times {10}^{20}$

  2. $6.0\times {10}^{19}$

  3. $6.0\times {10}^{18}$

  4. $6.0\times {10}^{17}$

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Correct Option: B
Explanation:
100 ml solution diluted to 1 liters (1000) ml contains $6.0 \times 10^{21}$ solute molecular

No of molecules present in 10 ml

$ = \dfrac{10 \times 6.0 \times 10 ^{21}}{1000} = 6 \times 10 ^{19} $

Highly pure dilute solution of sodium in liquid ammonia:

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. on evaporation yield metals.

  2. exhibits electrical conductivity.

  3. produces sodium amide and hydrogen gas instantly.

  4. acts as powerful reducing agent.

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Correct Option: A,B,D
Explanation:

$M+(x+y)NH _3\rightarrow [M(MH _3) _x]^++[4(NH _3) _y]^-$. Blue colour of the solution is due to ammoniated electrons and good conductor of electricity because of both ammoniated cations and ammoniated electrons.

The compound whose 0.1 ml solution isbasic is :

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. Ammonium acetate

  2. Ammonium chloride

  3. Ammonium sulphate

  4. Sodium acetate

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Correct Option: B

Homogeneous system among the following is

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. milk

  2. sand in water

  3. urea in water

  4. benzene in water

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Correct Option: C
The phenol-water system has a upper critical solution temperature.
chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. True

  2. False

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Correct Option: A
Explanation:

The given statement is true.
The phenol-water system has a upper critical solution temperature.
Above this temperature, the components of phenol-water system are miscible in all proportions.
The upper critical solution temperature is an upper limit to a temperature range of partial miscibility, or miscibility for certain compositions only.

When some liquid evaporates, the average speed of the molecules remaining will .......... .

chemistry mix and separate different types of solutions various mixtures introduction to solutions

  1. Increase because the more energetic molecules have left

  2. Decrease because the more energetic molecules have left

  3. Remain unchanged because all molecules have about the same speed

  4. Increase because there are fewer molecules

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Correct Option: B
Explanation:

Answer is B.

A liquid is comprised of molecules that are in constant motion, traveling at different rates. The average speed of these particles depends on the liquids temperature.  A rise in temperature increases molecular velocity as well as aggregate kinetic energy.  If molecules gain enough energy, their fast-moving particles will begin to bump against their neighbors.  Eventually, particles near the liquids surface will impart sufficient speed, and therefore sufficient kinetic energy, to cause the surface particles to propel away from the liquid in the form of gaseous molecules or, more simply, as water vapor.
As the particles with the highest kinetic energy levels evaporate, the average kinetic energy of the remaining liquid (sweat) decreases.  Because a liquids temperature is directly related to the average kinetic energy of its molecules, the liquid cools as it evaporates.
Hence, when some liquid evaporates, the average speed of the molecules remaining will decrease because the more energetic molecules have left.