Question

Which of the following solids would possess the lowest melting point?

C25H52

Hg

CaCl2

CuO

Answer 1

Answer: Hg

Explanation: As we know that in case of hydrocarbons, as the size increases, vander waal forces become strong thus attract each other with a strong tendency thus C_{25}H_{52} is solid at room temperature. Its melting point is approximately 50°C.

Mercury is the only metal which exist as liquid at room temperature thus iy has lower melting point of -38.83 °C.

CaCl2 is and CuO are closely packed solids and thus have high melting point. The former one has melting point of 772 °C and th latter one has melting point of 1326°C.

Thus Mercury has lowest melting point out of the given options.

Answer 2

The melting points of the compounds from the choices are listed below:

a. C25H52 -> +47 to +56 degrees celsius

b. Hg -> -38.83 degrees celsius

c. CaCl2 -> +772 degrees celsius

d. CuO -> +1326 degrees celsius

It is evident from the listed melting points above that mercury (Hg) has the lowest melting point. This is why mercury is liquid at room temperature.