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प्रश्न
Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.
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उत्तर
Two observations that may suggest that a chemical reaction has taken place are
(i) evolution of a gas and
(ii) change in temperature.
For example, zinc granules react with dilute sulphuric acid to evolve hydrogen gas, which is easily observed by the bubbles of hydrogen gas appearing around zinc granules. Also, the flask becomes hot, which shows heat is evolved during the reaction—that is, change in temperature.
Zn + H2SO4 → ZnSO4 + H2↑ + Heat
संबंधित प्रश्न
Write complete balanced equation for the following reaction:
Sulphur dioxide (gas) + Oxgyen (gas) 
Sulphur trioxide (gas)
When hydrogen is passed over copper oxide, copper and steam are formed. Write a balanced equation for this reaction and state which of the chemicals are metals.
Convey the following information in the form of a balanced chemical equation:
"An aqueous solution of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form a precipitate of ferrous hydroxide and sodium sulphate remains in solution."
Balance the following chemical equation:
MnO2 + HCI → MnCI2 + CI2 + H2O
One of the following does not happen during a chemical reaction. This is:
(a) Breaking of old chemical bonds and formation of new chemical bonds
(b) Formation of new substances with entirely different properties
(c) Atoms of one element change into those of another element to form new products.
(d) A rearrangement of atoms takes place to form new products.
Explain the following reaction with one suitable example .
Decomposition reaction
Balance the following equation .
N2 + O2 → NO
Balance the following equation. Also name the product formed.
N2 + H2 → NH3
Write down what you understood from the following chemical reaction.
AgNO3(aq) + NaCI(aq) → AgCI ↓ + NaNO3(aq)
Balance the following equation:
PbO + NH3 → Pb + H2O + N2
Write the balanced chemical equation of the following reaction. potassium bicarbonate + sulphuric acid → potassium sulphate + carbon dioxide + water
Write the balanced chemical equation of the following reaction.
sulphur + nitric acid→ sulphuric acid + nitrogen dioxide + water.
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate moles of chlorine gas formed.
1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the products formed in each case.
Balance the following simple equation:
Al + N2 → AlN
Balance the following simple equation:
Zn + HCl → ZnCl2 + H2
Balance the following simple equation:
NaOH + Cl2 → NaCl + NaClO + H2O
Write a balanced equation for the following word equation:
Potassium bicarbonate → Potassium carbonate + Water + Carbon dioxide
The following reaction is an example of a `4"NH"_3("g") + "SO"_2 -> 4"NO"("g") + 6"H"_2"O"("g")`
- displacement reaction
- combination reaction
- redox reaction
- neutralisation reaction
Which of the following are exothermic processes?
- Reaction of water with quick lime
- Dilution of an acid
- Evaporation of water
- Sublimation of camphor (crystals)
