Page 49 - NCERT Science Class 10 English Medium

Metal + Dilute acid → Salt + Hydrogen
But do all metals react in the same manner? Let us find out.

Activity 3.113.11
Activity 3.11
Activity 3.11
Activity
Activity 3.11
n Collect all the metal samples except sodium and potassium again.
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.
n Put the samples separately in test tubes containing dilute
hydrochloric acid.
n Suspend thermometers in the test tubes, so that their bulbs are
dipped in the acid.
n Observe the rate of formation of bubbles carefully.
n Which metals reacted vigorously with dilute hydrochloric acid?
n With which metal did you record the highest temperature?
n 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.
Hydrogen gas is not evolved when a metal reacts with nitric acid. It is
because HNO is a strong oxidising agent. It oxidises the H produced to
3 2
water and itself gets reduced to any of the nitrogen oxides (N O, NO,
2
NO ). But magnesium (Mg) and manganese (Mn) react with very dilute
2
HNO to evolve H gas.
3 2
You must have observed in Activity 3.11, that the rate of formation
of bubbles was the fastest in the case of magnesium. The reaction was
also the most exothermic in this case. The reactivity decreases in the
order Mg > Al > Zn > Fe. In the case of copper, no bubbles were seen and
the temperature also remained unchanged. This shows that copper does
not react with dilute HCl.
ou Know? 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
Do Y corrosive, fuming liquid. It is one of the few reagents that is able to dissolve gold and
platinum.

3.2.4 How do Metals react with Solutions of other Metal
Salts?

Activity 3.12
Activity
Activity 3.12
Activity 3.12
Activity 3.123.12
n Take a clean wire of copper and an iron nail.
n Put the copper wire in a solution of iron sulphate and the iron
nail in a solution of copper sulphate taken in test tubes (Fig. 3.4).
n Record your observations after 20 minutes.

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