Explanation

In the lab, oxygen gas is prepared by heating potassium chlorate (KClO₃) in the presence of manganese dioxide (MnO₂) as a catalyst.

MnO₂ speeds up the decomposition of KClO₃ without being consumed.

Explanation

• In a sample of a substance, the particles (atoms or molecules) have a distribution of energies at any given temperature. This is known as the Maxwell-Boltzmann distribution.
• According to this distribution, some particles have high energies, while others have low energies, but the average energy of the particles is constant at a given temperature.
• The energy of individual particles in a sample is not the same, as they are in constant motion and colliding with each other, leading to a range of energies.
• This is why the concept of average energy or kinetic energy is used to describe the energy of a sample as a whole.

Explanation

A diode is made by joining P-type and N-type doped semiconductors to form a PN junction, which allows current to flow in only one direction.

Explanation

Sodium (Na) always shows valency = 1, as it loses one electron to form Na⁺.

Iron (Fe) and Hydrogen (H) show variable valencies, while sodium’s valency remains unchanged.

Explanation

According to most sources, Iodine (I2) has the strongest intermolecular forces of attraction 

Iodine (I2):

Due to its large size and high number of electrons,

Iodine experiences the strongest London dispersion forces,

Which are the only type of intermolecular force present in nonpolar molecules like I2.

These forces are relatively weak compared to other types of intermolecular forces,

But in the case of large molecules like iodine, they become significant enough to result in a high boiling point. 

Explanation

Water is composed of atoms from two elements: hydrogen and oxygen.

A single water molecule (H₂O) consists of two hydrogen atoms and one oxygen atom, chemically bonded together. 

Hydrogen (H): Each water molecule has two hydrogen atoms.

Oxygen (O): Each water molecule has one oxygen atom.

Explanation

Helium  and Argon is a noble gas, part of Group 18 in the periodic table.

Helium (He)

The lightest noble gas, helium is used in hot air balloons and airships.

It's also used in air containers for deep-sea divers.

Argon (Ar)

Argon makes up 0.93% of the Earth's atmosphere.

It can be prepared by fractional distillation of liquid air.

Explanation

The Haber process uses nitrogen gas and hydrogen gas to manufacture ammonia.

Nitrogen is obtained from the air, while hydrogen is typically derived from natural gas. 

Explanation

- pH is a measure of the hydrogen ion concentration [H^+] in a solution.

- At 25°C, pure water undergoes auto-ionization:

  - H₂O ⇌ H⁺ + OH⁻

  - The concentrations of H⁺ and OH⁻ are both 1 × 10⁻⁷ mol/L.

- Using the formula:  

  pH = -log[H⁺]  

  pH = -log(1 × 10⁻⁷) = 7

Explanation

 The photoelectric effect was discovered by German physicist Heinrich Rudolf Hertz in 1887