Which vitamin is produced in the skin on exposure to sunlight?
A. Vitamin A
B. Vitamin D
C. Vitamin C
D. Vitamin B12
Correct Answer: B UV rays convert 7-dehydrocholesterol to Vitamin D in the skin.
Q2. Chemistry
Which gas is produced when zinc reacts with dilute HSO?
A. Oxygen
B. Chlorine
C. Hydrogen
D. Carbon dioxide
Correct Answer: C Zn + HSO -> ZnSO + H->. Hydrogen gas is produced.
Q3. Physics
What is the unit of measurement for entropy?
A. Joule
B. Joule per Kelvin
C. Kelvin
D. Newton
Correct Answer: B Entropy is measured in units of Joule per Kelvin (J/K).
Q4. Physics
The reason of mirage in desert is:
A. Reflection
B. Total internal reflection
C. Diffraction
D. Interference
Correct Answer: B Mirage occurs due to total internal reflection of light in layers of different refractive indices.
Q5. Chemistry
Which of the following has covalent bonding?
A. NaCl
B. HO
C. KBr
D. CaO
Correct Answer: B HO has covalent bonds (sharing of electrons). NaCl, KBr, CaO are ionic.
Q6. Chemistry
The most stable allotrope of carbon is:
A. Diamond
B. Graphite
C. Fullerene
D. Coal
Correct Answer: B Graphite is the most stable allotrope of carbon at room temperature.
Q7. Chemistry
The bond angle in water is approximately:
A. 90 degrees
B. 109.5 degrees
C. 104.5 degrees
D. 120 degrees
Correct Answer: C Water has bent shape with 104.5 degrees angle due to lone pair repulsion.
Q8. Physics
A wire of length L and area A has resistance R. If length is halved and area doubled, new resistance is:
A. R/2
B. R/4
C. R
D. 2R
Correct Answer: B R' = (L/2)/(2A) = (L/A)/4 = R/4.
Q9. Physics
The work done in moving a charge of 5 C across two points with potential difference 10 V is:
A. 2 J
B. 15 J
C. 50 J
D. 5 J
Correct Answer: C W = QV = 5 x 10 = 50 J.
Q10. Chemistry
The number of oxygen atoms in 1 mole of HSO is:
A. 4 x 6.022 x 10^2
B. 6.022 x 10^2
C. 2 x 6.022 x 10^2
D. 7 x 6.022 x 10^2
Correct Answer: A 1 molecule of HSO has 4 O atoms. 1 mole has 4 x NA = 4 x 6.022 x 10^2 atoms.
Q11. Biology
During DNA replication, which enzyme is responsible for synthesizing the new DNA strand by adding nucleotides complementary to the template strand?
A. DNA ligase
B. DNA helicase
C. DNA polymerase
D. Primase
Correct Answer: C During DNA replication, several enzymes play crucial roles:
* **DNA ligase:** Joins the Okazaki fragments on the lagging strand by forming phosphodiester bonds.
* **DNA helicase:** Unwinds the DNA double helix by breaking the hydrogen bonds between complementary base pairs, creating the replication fork.
* **DNA polymerase:** This is the primary enzyme responsible for synthesizing new DNA strands. It adds deoxyribonucleotides one by one to the growing DNA strand, using the existing template strand as a guide to ensure complementary base pairing (A with T, G with C).
* **Primase:** Synthesizes short RNA primers, which are necessary for DNA polymerase to initiate DNA synthesis, as DNA polymerase cannot start a new strand from scratch.
Q12. Physics
Which of the following has the highest specific heat capacity?
A. Iron
B. Copper
C. Water
D. Lead
Correct Answer: C Water has the highest specific heat capacity (4200 J/kg degrees C) among common substances.
Q13. Chemistry
Which of the following reagents would distinguish between ethanal and propanone?
A. Tollen's reagent
B. Fehling's solution
C. Benedict's solution
D. All of the above
Correct Answer: D Ethanal (CH3CHO) is an aldehyde, while propanone (CH3COCH3) is a ketone. Aldehydes can be easily oxidized to carboxylic acids by mild oxidizing agents, whereas ketones are generally resistant to oxidation by mild agents. Tollen's reagent (ammoniacal silver nitrate), Fehling's solution (alkaline solution of CuSO4 and sodium potassium tartrate), and Benedict's solution (alkaline solution of CuSO4 and sodium citrate) are all mild oxidizing agents used to detect aldehydes.
Ethanal, being an aldehyde, will give a positive test with Tollen's reagent (forming a silver mirror), Fehling's solution (forming a red precipitate of Cu2O), and Benedict's solution (forming a red precipitate of Cu2O).
Propanone, being a ketone, will not react with any of these mild oxidizing agents.
Therefore, all the listed reagents can distinguish between ethanal and propanone.
Q14. Physics
When light of frequency is incident on a photocathode, the stopping potential is V. When light of frequency is incident on the same photocathode, the stopping potential is V. If V > V, which of the following relations is correct? (h is Planck's constant, e is the charge of an electron)
A. h( - ) = e(V - V)
B. h( - ) = e(V - V)
C. h( + ) = e(V + V)
D. h( / ) = e(V / V)
Correct Answer: A According to Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons (KE_max) is given by:
h = + KE_max
where h is Planck's constant, is the frequency of incident light, and is the work function of the metal.
The stopping potential (V_s) is related to KE_max by: KE_max = eV_s
So, the equation becomes: h = + eV_s
For the first case:
h = + eV (Equation 1)
For the second case:
h = + eV (Equation 2)
Subtract Equation 1 from Equation 2:
(h - h) = ( + eV) - ( + eV)
h( - ) = eV - eV
h( - ) = e(V - V)
Q15. Chemistry
The number of electrons in Na ion is:
A. 11
B. 10
C. 12
D. 9
Correct Answer: B Na (11 e) -> Na loses 1 e -> 10 electrons.