Explanation

Mr of MgCO₃ = 84  

Mr of MgO = 24 + 16 = 40  

Moles of MgCO₃ = 21.0 g ÷ 84 g/mol = 0.25 mol  

From equation: 1 mol MgCO₃ → 1 mol MgO  

So 0.25 mol MgCO₃ → 0.25 mol MgO  

Mass of MgO = 0.25 mol × 40 g/mol = 10.0 g

Last verified on 11-04-2026

Explanation

• Changes of state involve transformation between solid, liquid, and gas.
• Sublimation is a direct change from solid to gas.
• In this process, particles move from a fixed arrangement to widely spaced.
• No liquid phase is involved in between.
• This change is called sublimation.
• 
  

Last verified on 11-04-2026

Explanation

• X-rays are a form of electromagnetic radiation.
• They are produced in X-ray tubes.
• High-speed cathode rays (electrons) hit a solid target.
• The sudden stopping of electrons produces X-rays.
• The target is usually made of metal (like tungsten).

Last verified on 11-04-2026

Explanation

• Earth water coverage: 71%
• Land area: 29%
• Ocean water: 97% of total water
• Fresh water: 3% of total water
• Largest ocean: Pacific Ocean

Last verified on 10-04-2026

Explanation

• Proton ≈ 1 atomic mass unit (amu)
• Neutron ≈ 1 amu
• Electron ≈ 1/1836 of a proton

So, the Electron has the least mass.

Explanation

• Electron is a fundamental particle with much smaller mass than protons and neutrons.
• Proton and Neutron are roughly 1836 times heavier than an electron.
• Masses (approx.): Electron – 9.11×10⁻³¹ kg, Proton – 1.67×10⁻²⁷ kg, Neutron – 1.67×10⁻²⁷ kg.

Last verified on 03-04-2026

Explanation

• Glass and pitch are examples of pseudo solids.
• Pseudo solid is a solid which possesses the property of liquids.
• Glass is a pseudo solid and in a very slow process, it flows like a liquid due to which the base of glass gets thicker than top.

Last verified on 02-04-2026

Explanation

• The freezing (or melting) point of ice on the Fahrenheit scale is 32°F.
• This is the temperature at which ice turns from a solid to a liquid. 
• The Fahrenheit scale also defines the boiling point of water as 212°F.
• A change of 1°F on the Fahrenheit scale is less than a 1°C change on the Celsius scale.

Last verified on 02-04-2026

Explanation

• Geochemistry focuses on the chemical elements and compounds in Earth materials.
• It helps to understand rocks, minerals, and soil composition.

Last verified on 01-04-2026

Explanation

• Jabir ibn Hayyan, known as the "father of chemistry."
• He was an Arab Chemist.
• Composition of Alchemy was written by Jabir Bin Hayyan.

Notable ideas:

• Use of organic substances in chemistry
• Sulfur-mercury theory of metals
• Science of the balance
• Science of artificial generation

Last verified on 07-02-2026