Activity
Aim of the activity
To observe the reaction of zinc granules with dilute hydrochloric acid or sulphuric acid
Materials required
1. Zinc granules
2. Dilute hydrochloric acid
3. Dilute sulphuric acid
4. Matchstick
5. Test tubes
6. Test tube holder
7. Conical flask
Procedure
We will take a few zinc granules in a conical flask and add some dilute hydrochloric acid or sulphuric acid carefully and slowly.
Observation
When we add acid to zinc granules, we see the following
i.Bubble formation: - we can see effervescence around the zinc granules.
ii. Temperature change:- we can observe an increase in temperature by touching the conical flask.
iii. Gas test:- when we bring a burning matchstick near the mouth of the flask, we can hear a pop sound that indicates the hydrogen gas
Explanation
The reaction between zinc and dilute hydrochloric acid or sulphuric acid produces a salt zinc sulphate and hydrogen gas.
Chemical reaction between zinc and HCl
`Zn + HCl →ZnCl_2 + H_2↑`
Chemical reaction between zinc and H2SO4
`Zn + H_2SO_4 →ZnSO_4 + H_2↑`
This reaction is a displacement reaction. Zinc is more reactive than hydrogen, displacing hydrogen to form the acid.
Conclusion
Zinc reacts with dilute acids like `HCl` or `H_2SO_4` to produce hydrogen gas, the reaction is an exothermic reaction and also a displacement reaction.
Frequently Asked Questions
1. Why does the flask become warm during the activity?
Ans – The reaction between zinc granules and acids releases heat making the reaction exothermic.
2. How can we identify the gas that evolved during the reaction?
Ans – When we bring a burning matchstick or a candle near the flask, the gas burns with a ‘pop’ sound, this indicates that the gas is hydrogen gas.
3. Why does hydrogen gas make a pop sound
Ans – Hydrogen gas is highly inflammable so when it comes in contact with oxygen, it bursts with a pop sound.
4. What is the chemical formula of sulphuric acid?
Ans – `H_2SO_4`
5. What is the chemical of zinc sulphate?
Ans – `ZnSO_4`
6. What is an exothermic reaction?
Ans – The chemical reaction in which heat gets evolved or produced along with products, is called an exothermic reaction.
7. What is displacement reaction?
Ans – The chemical reaction in which a more reactive element displaces a less reactive element from the compound is known as a displacement reaction.
Important extra points
1. This is an example ofa displacement reaction.
2. The hydrogen gas is a highly flammable gas.
Application of hydrogen gas
2. As a fuel
3 . In synthesis of ammonia
Safety Precautions: -
1. Wear gloves and safety goggles to avoid contact with skin or eyes.
2. Proper ventilation should be maintained.
3 .Don’t use concentrated acids.
You can also explore
You can use different metals like magnesium, aluminium or iron to compare the rate of reaction with acids. You can make the reactivity series of metals.
Fun facts
Hydrogen gas is the lightest element in the universe and a major component of stars and the sun.
Zinc is used in galvanization to protect iron from rusting.
Multiple Choice Questions
1. What gas evolved during this activity?
a.Oxygen
b.Hydrogen
c.Carbon dioxide
d.Nitrogen
Correct answer – ( b) – Hydrogen
2. How can you identify that the chemical reaction is taking place in this activity?
a.Formation of bubbles
b.Change in colour
c.Formation of precipiatate
d.No change
Correct answer – (a)- Formation of bubbles
3. What sound is produced when the evolved gas is tested with a lit matchstick?
a.Whistling sound
b.Hissing sound
c.Pop sound
d.No sound
Correct answer –(c)
4.What type of reaction takes place between zinc and dilute acid?
a.Displacement reaction
b.Combination reaction
c.Decomposition reaction
d.Neutralization reaction
Correct answer –(a)
5. What are the main products formed when zinc and sulphuric acid?
a.Zinc and sulphur
b.Zinc sulphate and hydrogen
c.Zinc sulphate and oxygen
d.Zinc chloride and hydrogen
Correct answer –(c)
Related Topics for you
1. Solution of Chemical Reactions and Equations
3. Extra Questions of Chapter 1
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