Question

q.6. which one of the following is an element? a) gold b) water c) pure salt d) sea water q.7. which of these substances is a compound? a) pure water b) mercury c) iron d) salt water q.8. how many atoms are present in one molecule of glucose, c6h12o6? a) 3 b) 4 c) 12 d) 24 q.9. what kind of matter is carbon dioxide, co2? a) homogeneous mixture b) heterogeneous mixture c) compound d) element

Explanation:

• Q.6: Gold is an element as it consists of only one - type of atom. Sea water is a mixture, water is a compound, and pure salt is a compound.
• Q.7: Pure water ($H_2O$) is a compound made of hydrogen and oxygen atoms. Iron is an element, mercury is an element, and salt - water is a mixture.
• Q.8: In a glucose molecule ($C_6H_{12}O_6$), the number of atoms is calculated as $6 + 12+6=24$.
• Q.9: Carbon dioxide ($CO_2$) is a compound as it is made up of two different types of atoms (carbon and oxygen) chemically bonded together.

Answer:

Q.6: a) Gold
Q.7: a) Pure Water
Q.8: d) 24
Q.9: c) compound