Question

(i) Give two reasons to support the statement that CO2 is a compound and not a mixture. (ii) Classify the following as pure substance or a mixture. If mixture, indicate whether homogeneous or heterogeneous. (a) 24 carat gold (b) Air (c) Concrete.

Answer 1

(a) (i) Carbon and oxygen are present in a fixed ratio of 3 : 8 by mass in carbon dioxide.

(ii) The constituents of carbon dioxide cannot be separated by simple physical methods.

(b) (i) 24 carat gold is a pure substance.

(ii) Air is a homogeneous mixture in which the constituents are uniformly distributed through out without any clear boundary of separation.

(iii)Concrete is a heterogeneous mixture that does not have uniform constituents.

Answer 2

two reasons are as under
co2 is made up of two elements carbon and oxygen.
the ratio of carbon and oxygen are fixed in co2.
gold - pure substance
air - mixture - homogeneous
concrete - heterogeneous.