SPSC Chemistry 25 years Past Papers

Q21: If the wave length of photon is doubled _____?

اگر فوٹوون کی لہر کی لمبائی دوگنی ______ ہے؟

Energy is doubled

Frequency is doubled

Energy is reduced by the factor of two

None of these

Explanation

Energy of a photon is given by $E = frac{hc}{lambda}$ , so if the wavelength ( $lambda$ ) is doubled, energy ( $E$ ) is halved.

Frequency ( $f$ ) and wavelength ( $lambda$ ) are inversely related ( $c = flambda$ ), so doubling $lambda$ reduces $f$ by half.

Q22: The melting point of mercury is ______?

عطارد کا پگھلنے کا نقطہ ______ ہے؟

-39°C

0°C

-100°C

None of these

Q23: Which substance is known as Oil of Vitriol?

کون سا مادہ وٹریول کے تیل کے نام سے جانا جاتا ہے؟

Nitric acid

Hydrochloric acid

Phosphoric acid

Sulfuric acid

Q24: Which of the following instruments may be used to measure the optical activity of a compound?

کسی کمپاؤنڈ کی آپٹیکل سرگرمی کی پیمائش کے لئے مندرجہ ذیل میں سے کون سا آلات استعمال ہوسکتے ہیں؟

Polarimeter

Spectrophotometer

Calorimeter

None of these

Q25: Which of the following instrumental component is not required in atomic emission spectrometer?

جوہری اخراج اسپیکٹومیٹر میں مندرجہ ذیل میں سے کون سا آلہ کار جزو کی ضرورت نہیں ہے؟

Monochromator

Source of electromagnetic radiation

Detector

None of these

Q26: A gas is said to behave like an ideal gas when relation PV/T= Constant. When do you expect a real gas to behave like ideal gas?

When the temperature is high and pressure is low

When the temperature is low

When both the temperature and pressure are low

None of these

Explanation

A real gas behaves like an ideal gas at high temperature (molecules have enough kinetic energy to overcome intermolecular forces) and low pressure (molecules are far apart, reducing interactions).

Under these conditions, the gas follows the ideal gas equation $PV = nRT$ .

Q27: Which isotope of hydrogen is radioactive?

ہائیڈروجن کا کون سا آاسوٹوپ تابکار ہے؟

Tritium

Protium

Deuterium

None of these

Q28: Which of the following is not an electrophile?

مندرجہ ذیل میں سے کون سا الیکٹرو فائل نہیں ہے؟

AlCl₃

C₂H₅OCH₃

[CH₃]₃C⁺

None of these

Q29: Which one of the following is not a condensation polymer?

مندرجہ ذیل میں سے کون سا گاڑھاپن پولیمر نہیں ہے؟

Dacron

Melamine

Neoprene

None of these

Q30: The atom formed by the beta decay of carbon-14 is _____?

Nitrogen-14

Boron-14

Oxygen-14

None of these