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What happens when Metals react with Acids?

We have already learnt that metals react with acids to give a salt and hydrogen gas. Metal + Dilute acid → Salt + Hydrogen But do all metals react in the same manner? Let us find out. Collect all the metal samples except sodium and potassium again. Mg, Zn, Cu, Fe, Al If the samples are tarnished, rub them clean with sand paper.

CAUTION: Do not take Sodium and Potassium as they react vigorously even with cold water. Put the samples separately in test tubes containing dilute Hydrochloric acid. Suspend thermometers in the test tubes, so that their bulbs are dipped in the acid. *Observe the rate of formation of bubbles carefully. *Which metals reacted vigorously with dilute hydrochloric acid? *With which metal did you record the highest temperature? Arrange the metals in the decreasing order of reactivity with dilute acids.

Write equations for the reactions of Magnesium, Aluminium, Zinc and Iron with dilute hydrochloric acid. Mg + 2HCl---------- MgCl2 +H2 2 Al + 6 HCl---------- 2AlCl3 + 3H2 Zn +2HCl---------- ZnCl2 + H2 2Fe +6HCl-------- 2FeCl3 + 3H2 *Copper does not react with dilute HCl.

Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2). But Magnesium (Mg) and Manganese (Mn) react with very dilute HNO3 to evolve H2 gas.

if the solution is very dilute: Mg + 2HNO3-------- Mg(NO3)2 + H2 At moderate concentrations (and even with very dilute acid, this will happen to some extent): 3Mg +8HNO3-------- 3 Mg(NO3)2 + 2NO + 4H2O And with concentrated acid: Mg + 4HNO3-------- Mg(NO3)2 + 2NO2 + 2H2O

Do you know….. Aqua regia Aqua regia, (Latin for ‘royal water’) is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It can dissolve gold, even though neither of these acids can do so alone. Aqua regia is a highly corrosive, fuming liquid. It is one of the few reagents that is able to dissolve gold and platinum.

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