Science (English Medium) कक्षा १२ - CBSE Important Questions

List any four techniques where the principle of ex-situ conservation of biodiversity has been employed.

Identify ‘a’ and ‘b’ in the figure given below representing proportionate number of major vertebrate taxa.

Why should we conserve biodiversity ? How can we do it?

'in-situ' Conservation can help endangered/threatened species. Justify the statement.

Name and describe any three causes of bio-diversity losses.

Explain the concept of "co-extinction" by taking two examples.

List any three major causes of loss of biodiversity.

Enlist two criteria that are used to identify a region for maximum protection as 'Biodiversity hotspots'.

"Forests provide intangible benefits to us." Explain by taking three different areas, how.

The IUCN Red Data List (2004) in the last 500 years documents the extinction of nearly 784 species including ______.

What is ferromagnetism?

What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction?

An element crystallizes in a f.c.c. lattice with a cell edge of 250 pm. Calculate the density if 300 g of this element contains 2 × 10²⁴ atoms. 

Calculate the freezing point of solution when 1.9 g of MgCl₂ (M = 95 g mol⁻¹) was dissolved in 50 g of water, assuming MgCl₂ undergoes complete ionization.

(K_f for water = 1.86 K kg mol⁻¹)

Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why?

What happens when the external pressure applied becomes more than the osmotic pressure of solution?

When 2.56 g of sulphur was dissolved in 100 g of CS₂, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (S_x).

(K_f for CS₂ = 3.83 K kg mol⁻¹, Atomic mass of sulphur = 32 g mol⁻¹]

Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing

(i) 1.2% sodium chloride solution?

(ii) 0.4% sodium chloride solution?

What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3^rd of tetrahedral voids?

What is meant by positive deviations from Raoult's law? Give an example. What is the sign of ∆_mixH for positive deviation?