NEET Practice Questions

Step: Find the resultant pressure of the gas.
The pressure of the gas is given by; 
\(P=\frac{1}{3}\frac{mN}{V}v^{2}_{rms}\)
When the mass of the gas molecules is halved and their rms speed is doubled then the resultant pressure of the gas is; 
\(P’=\frac{1}{3}\frac{\left(\frac{m}{2}\right)N}{V}(2v)^{2}_{rms}= \frac{4}{2}\times \frac{1}{3}\frac{mN}{V}v^{2}_{rms}\)
\(\Rightarrow P’ = 2P\)
Hence, option (1) is the correct answer. 
 

Step: Find the amount of energy required to bring the charges closer.
Electrostatic potential energy between two charges separated by distance \(r\) is given by;
\(U = \frac{kq_1q_2}{r}\) 
Initial electrostatic potential energy between the charges is given by;
\(U_i = \frac{9\times 10^9 \times 1.1 \times 10^{-8}\times 1.1\times 10 ^{-9}}{0.1} = 10.89 \times 10^{-7}~\text{J}\)
The final electrostatic potential energy between the charges is given by;
\(U_f = \frac{9\times 10^9 \times 1.1 \times 10^{-8}\times 1.1\times 10 ^{-9}}{0.01} = 10.89 \times 10^{-6}~\text{J}\)
The amount of energy required to bring the charges closer is given by;
\(\Rightarrow W = U_f-U_i = 10.89\times10^{-6}[1-0.1] \)
\(\Rightarrow W = 10.89\times10^{-6}\times0.9 \approx 10^{-5}~\text{J}\)
Hence, option (4) is the correct answer
 

Step: Identify the equations of given waves.
\(Y_{A}=A\sin\omega t \\ Y_{B}=A\sin\left ( \omega t+\pi /2 \right ) \\ Y_{C}=A\sin\left ( \omega t-\pi /2 \right )\)
So, from above, it is clear that the wave \(C\) lags behind in phase by \(\pi/2\) and \(B\) leads by \(\pi/2\).
Hence, option (1) is the correct answer.
 

Hint: A is an alkene

In the first reaction, when vicinal dibromide reacts with Zn then alkene is obtained as a product. In the next step, alkene reacts with diborane followed by basic hydrogen peroxide give alcohol as a product. 

The reaction is known as the Hydroboration Oxidation reaction. The reaction follows the Anti-Markovnikov rule. The reaction is as follows:

Hence, option third is the correct answer. 
 

Hint: The shape of ammonia is trigonal pyramidal.

Explanation: 

At room temperature, ammonia is a colorless gas with a very pungent odor. This odor is familiar to many people because ammonia is used commonly in cleaning products and smelling salts.

Nitric acid is produced by the oxidation of ammonia. The liquid ammonia is evaporated, superheated, and sent with compressed air to a convertor, containing platinum and rhodium catalyst.

NH₃/NH₄OH is used to precipitate the hydroxides of many metals from their salt solutions.

The shape of ammonia is trigonal pyramidal and not trigonal planar. 3 bond pairs and one lone pair are present in NH₃. The bond angle is 107° approx.

Explanation: 

Borax on heating loses water of crystallisation and swells to form a puffy mass which further heating melts to give a clear liquid which solidifies to a transparent glass like bead consist of sodium metaborate NaBO₂ and boric anhydride B₂O₃.

Borax bead test is used to identify the nature of cation present in solution by observing the colour of the bead. The color and bead of copper formed during its borax bead test in a hot oxidizing flame is Green when hot and blue when cold.

The reaction is as follows: 

\(Na_2B_4O_7\xrightarrow{\text{ heat }~~}\,B_2O_3+NaBO_2 \)

So, option 2 is the correct answer.