1.

The number of tripeptides formed by three different amino acids using each amino acid once is ______.

2.

$\textbf{Choose the correct statements about the hydrides of group 15 elements.}$
A. The stability of the hydrides decreases in the order \(\text{NH}_3 > \text{PH}_3 > \text{AsH}_3 > \text{SbH}_3 > \text{BiH}_3\)
B. The reducing ability of the hydrides increases in the order \(\text{NH}_3 < \text{PH}_3 < \text{AsH}_3 < \text{SbH}_3 < \text{BiH}_3\)
C. Among the hydrides, \(\text{NH}_3\) is a strong reducing agent while \(\text{BiH}_3\) is a mild reducing agent.
D. The basicity of the hydrides increases in the order \(\text{NH}_3 < \text{PH}_3 < \text{AsH}_3 < \text{SbH}_3 < \text{BiH}_3\)
Choose the most appropriate from the option given below:

• A and B only
• C and D only
• B and C only
• A and D only

3.

Following Kjeldahl's method, 1g of organic compound released ammonia that neutralized 10 mL of 2M H\(_2\)SO\(_4\). The percentage of nitrogen in the compound is _________.%.

4.

If each term of a geometric progression \( a_1, a_2, a_3, \dots \) with \( a_1 = \frac{1}{8} \) and \( a_2 \neq a_1 \), is the arithmetic mean of the next two terms and \( S_n = a_1 + a_2 + \dots + a_n \), then \( S_{20} - S_{18} \) is equal to

• \( 2^{15} \)
• \( -2^{18} \)
• \( 2^{18} \)
• \( -2^{15} \)

5.

A body of mass 1000 kg is moving horizontally with a velocity of 6 m/s. If 200 kg extra mass is added, the final velocity (in m/s) is:

• 5 m/s
• 4 m/s
• 2 m/s
• 6 m/s

6.

The amount of electricity in Coulomb required for the oxidation of 1 mol of \( \text{H}_2\text{O} \) to \( \text{O}_2 \) is \[\_ \times 10^5 \, \text{C}.\]