SPSC 25 years Past Papers 2001 to 2025

Q1851: A Carnot engine whose sink is at 300K has an efficiency of 40%. By how much should the temperature source be increased so as to increase its efficiency by 50% of original efficiency?

275K

325K

250K

None of these

Q1852: The children could not stop ____?

Laughing

Laugh

Laughed

None of these

Q1853: Ignition of Fe(OH)₃ to give Fe₂O₃ is called?

Dehydration

Evaporation

Filtration

None of these

Q1854: The carbon atoms in ethyne C2H2 are said to be _______?

sp^2-hybridzed

sp^3-hybridzed

sp-hybridzed

None of these

Q1855: The kinetic energy of an electron ejected from a metal surface exposed to monochromatic radiation depends on the at _____?

ایک الیکٹران کی حرکیاتی توانائی جو دھات کی سطح سے نکالی گئی ہے جو مونوکرومیٹک تابکاری کے سامنے ہے _____ پر منحصر ہے؟

Wavelength of the light used

Intensity of the light used

Frequency of the light used

None of these

Q1856: Raman spectra may be obtained in _____?

رامان سپیکٹرا _____ میں حاصل کیا جاسکتا ہے؟

UV and Visible region

IR and Visible region

IR and Microwave region

None of these

Q1857: A substituent effect on the organic compound due to permanent polarity of the group is called ______?

گروپ کی مستقل قطعیت کی وجہ سے نامیاتی کمپاؤنڈ پر متبادل اثر ______ کہا جاتا ہے؟

Chelate Effect

Inert Pair Effect

Inductive Effect

None of these

Q1858: Ionic hydrides are formed by elements of ______?

آئنک ہائیڈرائڈز ______ کے عناصر کے ذریعہ تشکیل پاتے ہیں؟

Group-IA

Group-IIIA

Group-IIA

None of these

Q1859: Elements of S-block all have configurations ______?

ایس بلاک کے ____ عناصر سب کی تشکیلات ہیں؟

ns^3 ns^4

ns^3/ns^4

ns^1/ns^2

None of these

Q1860: The critical temperature of water is higher than O2, because the H2O molecules have ______?

Dipole moment

Fewer electrons than O2

Two covalent bonds

None of these

Explanation

Water ( $H_2O$ ) has a high dipole moment, leading to strong hydrogen bonding between molecules.

This increases its critical temperature compared to $O_2$ , which has weak intermolecular forces.