Q. After $2$ hours the amount of a certain radioactive substance reduces to $1/6^{th}$ of the original amount (the decay process follows first-order kinetics). The half-life of the radioactive substance is:

1. $15$ min
2. $30$ min
3. $45$ min
4. $60$ min

Q. An isolated box, equally partitioned contains two ideal gases $A$ and $B$ as shown. When the partition is removed, the gases mix. The changes in enthalpy $\left(\Delta H\right)$ and entropy $\left(\Delta S\right)$ in the process, respectively, are:

1. zero, positive
2. positive, zero
3. zero, negative
4. negative, zero

Q. In the given set of aromatic compounds, the correct order of reactivity toward Friedel-Crafts alkylation is:

1. i > ii > iii > iv
2. ii > iv > iii > i
3. iv > ii > iii > i
4. iii > i > iv > ii

Q. The set of principal $\left(n\right)$, azimuthal $\left(l\right)$ and magnetic $\left(m_l\right)$ quantum numbers that is not allowed for the electron in $H$-atom is:

1. $n=3,l=1,m_1=-1$
2. $n=3,l=0,m_1=0$
3. $n=2,l=1,m_1=0$
4. $n=2,l=2,m_1=-1$

Q. A compound that shows positive iodoform test is:

1. 2-pentanone
2. 3-pentanone
3. 3-pentanol
4. 1-pentanol

Q. The solubility curve of $KN{O}_3$ in water is shown below.
The amount of $KN{O}_3$ that dissolves in $50g$ of water at $40$ is closest to:

1. $100g$
2. $150g$
3. $200g$
4. $50g$

Q. Two balloons $A$ and $B$ containing $0.2$ mole and $0.1$ mole of helium at room temperature and $2.0$ atm, respectively, are connected. When equilibrium is established, the final pressure of $He$ in the system is:

1. $1.5$ atm
2. $0.5$ atm
3. $1.0$ atm
4. $2.0$ atm

Q. In the conversion of a zinc ore to zinc metal, the process of roasting involves:

1. $ZnS\to ZnO$
2. $ZnC{O}_3\to ZnO$
3. $ZnS\to ZnS{O}_4$
4. $ZnO\to ZnS{O}_4$

Q. At $298K$, assuming ideal behaviour, the average kinetic energy of a deuterium molecule is:

1. two times that of a hydrogen molecule
2. four times that of a hydrogen molecule
3. same as that of a hydrogen molecule
4. half of that of a hydrogen molecule

Q. The gas produced from thermal decomposition of ${\left(N{H}_4\right)}_2{Cr}_2{O}_7$ is:

1. Nitrogen
2. Oxygen
3. Nitric oxide
4. Ammonia