Question

Identify each sample of solid based on the experimental data given. (4 marks) Sample A Sample B -50 2800 Approximate Melting point (°C) Solubility in Water Insoluble Soluble Conductivity of solid Good None but conducts in solution Sample ID: Possible Samples: • Sugar (CH-206) • Graphene • Gold • Mgo • Hg • dry ice (CO2(s))

Answer 1

A. Sample A conducts electricity in solid state. Out of the above options, we see that the property of electrical conductivity is shown by Gold and Mercury (Hg), since both are metal, (Metals conduct electricity in solid as well as molten state). Graphene also conducts electricity because of its structure where there is an unbounded electron which is free to move in the structure.
Now out of these three, we know that Graphene is a molecular solid and an allotrop of Carbon, it has very very high melting point. Also Gold is a metal having high melting point. But we know that Mercury is liquid at room temperature. Hence out of these, the element having least melting point is Mercury.
Hence Sample A = Mercury (Hg).

B. In case of sample B, we see that it is soluble in water. Thus we conclude that it can be either Sugar, MgO or Dry Ice (Carbon Dioxide). Metals are not soluble in water, they can only be melted. Graphene is also not soluble in water just like diamond.
Out of these three, Sugar and Dry Ice both are organic componds, they neither conduct electricity in solid state nor when dissolved in water. On the other hand, when we dissolve MgO in water, it forms Mg²⁺ and O^2- ions. These ions conduct electricity.
Hence Sample B = MgO