Q. An ideal gas initially at temperature $T_{1}$ with $\gamma =5/3$ expands adiabatically into vacuum to double its volume. The final temperature $T_{2}$ is given by:

NTA AbhyasNTA Abhyas 2020 Report Error

A

$T_{2}=T_{1}\times \left(\right.0.5\left(\left.\right)^{2 / 3}$

B

$T_{2}=T_{1}$

C

$T_{2}=T_{1}\left(\right.2\left(\left.\right)^{- 1 / 3}$

D

$T_{2}=\frac{T_{1}}{2}$

Solution:

For adiabatic expansion against vacuum.
$q=0w=0,\because P_{ext}=0$
$ΔU=q+w$
$ΔU=0$
$\Rightarrow nC_{vm}ΔT=0\Rightarrow ΔT=0$
$T_{1}=T_{2}$

Questions from NTA Abhyas 2020

1. Which reaction is suitable for preparing $\alpha $ -Chloroacetic acid?

2. A mixture of methane and ethene in a molar ratio of $x:y$ has an average molecular mass of $20 u$ . The mean molar mass when they are mixed in the molar ratio of $y:x$ will be -

Some Basic Concepts of Chemistry

3. For a given reaction, energy of activation for forward reaction $E _{ af }$ is $80 kJ mol ^{-1}$ and $\Delta H =-40 kJ mol ^{-1}$. A catalyst lowers $E _{ af }$ to $20 kJ mol ^{-1}$. The ratio of energy of activation for reverse reaction before and after addition of catalyst is:

Chemical Kinetics

4. 3 Faradays of electricity was passed through an aqueous solution of iron (II) bromide. The weight of iron metal (at. wt. = 56) deposited at the cathode (in g) is

Electrochemistry

5. Cyclohexene on ozonolysis followed by reaction with zinc dust and water gives compound E and compound E on further treatment with aqueous KOH yields compound F. Then compound F is

Aldehydes Ketones and Carboxylic Acids

Chemistry Most Viewed Questions

1. If for a certain reaction $\Delta_{r}H$ is $30\, kJ\, mol^{-1}$ at $450 \,K$, the value of $\Delta_{r}S$ (in $JK^{-1}\, mol^{-1})$ for which the same reaction will be spontaneous at the same temperature is

NEET 2020

2. If $8\,g$ of a non-electrolyte solute is dissolved in $114\, g$ of n-octane to reduce its vapour pressure to $80\%$, the molar mass (in $g \,mol^{-1})$ of the solute is [Given that molar mass of n-octane is $114 \,g\, mol^{-1}]$

NEET 2020 Solutions

3. An organic compound contains $78 \%$ (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is: [Atomic wt. of $C$ is $12, H$ is $1$]

NEET 2021 Some Basic Concepts of Chemistry

4. At standard conditions, if the change in the enthalpy for the following reaction is $-109 \,kJ\, mol^{-1}$ $H_{2(g)}+Br_{2(g)} \to 2HBr_{(g)}$ Given that bond energy of $H_{2}$ and $Br_{2}$ is $435\,KJ\,mol^{-1}$ and $192\,KJ\,mol^{-1}$ , respectively, what is the bond energy (in $KJ \,mol^{-1})$ of $HBr$ ?

NEET 2020

5. The density of 2 M aqueous solution of NaOH is 1.28 g/cm$^3$. The molality of the solution is
[Given that molecular mass of NaOH = 40 g mol$^{-1}$]

NEET 2019 Some Basic Concepts of Chemistry

Latest Updates