Mixture of which one of the following pairs of gases is the cause of occurrence of most of the explosions in mines?

Match List I with List II and select the correct answer using the codes given below the lists.
List I                              List II
A. German silver       1. Tin
B. Solder                     2. Nickel
C. Bleaching powder3. Sodium
D. Hypo                      4. Chlorine

Hard water is water that has high mineral content. Consider the following statements Hard water is not suitable for
(a) drinking
(b) washing clothes with soap
(c) use in boilers
(d) irrigating crops
Which of these statements are correct?

What are Rubies and Sapphires chemically known as?

Which one of the following is the correct sequence in increasing order of molecular weights of the hydrocarbons?

An aqueous solution of copper sulphate is acidic in nature because the salt undergoes

Corrosion is  electro-chemical oxidation of metals in reaction with an oxidant such as  oxygen. Aluminium surface are often' anodized'. This means the deposition of a layer of