Q7.Elements of which group are known as ore forming elements?
Answer : Option DExplaination / Solution:
Maximum number of ores contain group16 elements (O, S etc). They are known as "chalcogens" which was derived from the Greek word chalcos , meaning "ore formers," since they all are be found in copper ores.
Q9.The thermal stability of hydrides of group 16 elements decreases in the order
Answer : Option AExplaination / Solution:
As we move down the group bond length increases and bond enthalpy for the dissociation of H-E bond decreases. Due to decrease in enthalpy the thermal stability of hydrides decreases down the group.