Reasons of alloys as mixtures

Reasons of alloys as mixtures

Though the alloys are homogeneous mixture of metals which cannot be separated by any physical means, yet they are regarded mixtures on account of the following reasons :

• The composition of constituent metals can be varied in an alloy. For example, brass is an alloy of copper and zinc. If an alloy has 60% of copper and rest of zinc or 58% of copper and rest of zinc, in either case it is brass.
• The individual metals in any alloy retain their chemical and physical properties. For example, if brass is treated with dilute sulphuric acid, then zinc in it reacts to form zinc sulphate and hydrogen, but copper does not react

Ex.1 Classify the following into homogeneous or heterogeneous mixtures : Soda water, Wood, Air, Soil, Vinegar, Filtered tea.

Solution:  Homogeneous mixture: Soda water, Air, Vinegar, Filtered tea.

Heterogeneous mixture: Wood, Soil

Ex.2 Paints often need to be stirred thoroughly before use. Why?

Solution: Paints are suspensions. On keeping for longer periods, they tend to settle down. Therefore, to bring the settled particles in the colloidal state, paints are often stirred thoroughly before use.