Question : Which of the following metal salts is responsible for permanent hardness in water?

Option 1: KCl

Option 2: Nacl

Option 3: Ca(HCO₃)₂

Option 4: CaCl₂

Question : In 1830, which American scientist created the world's most powerful electromagnet, the Albany magnet, which could lift to 750 pounds of metal at a time?

Option 1: John Cockcroft

Option 2: William Gilbert

Option 3: Joseph Henry

Option 4: Edward Mills Purcell

Question : Which of the following statements is correct?

Option 1: Metals react with acids and produce metal salts and hydrogen gas.

Option 2: Non-metals react with oxygen to produce non-metallic oxides which are basic.

Option 3: On burning, metals react with oxygen to produce acidic metal oxides.

Option 4: Less reactive metals displace more reactive metals from their compounds in aqueous solutions.

Question : A metal ball and a rubber ball, both having the same mass, strike a wall normally with the same velocity. The rubber ball rebounds and the metal ball does not rebound. It can be concluded that:

Option 1: The rubber ball suffers a greater change in momentum

Option 2: The metal ball suffers a greater change in momentum

Option 3: Both suffer the same change in momentum

Option 4: The initial momentum of the rubber ball is greater than that of the metal ball

Question : Which s-block element is a silvery-white metal used in an alloy with copper or nickel to make gyroscopes, springs, electrical contacts, spot-welding electrodes and non-sparking equipment?

Option 1: Beryllium

Option 2: Rubidium

Option 3: Francium

Option 4: Caesium