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प्रश्न
Grills of doors and windows are always painted before they are used.
उत्तर
- Usually, grills of doors and windows are made of iron.
- Iron objects get rusted on exposure to moist air.
- Since air always contains moisture, iron grills get rusted.
- Painting iron objects prevents rusting, hence iron grills of doors and windows are painted before they are used.
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संबंधित प्रश्न
Balance the following chemical equation.
\[\ce{NaCl + AgNO3 -> AgCl + NaNO3}\]
Translate the following statement into chemical equation and then balance it.
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Write complete balanced equation for the following reaction:
Sulphur dioxide (gas) + Oxgyen (gas) 
Sulphur trioxide (gas)
Balance the following chemical equation:
MnO2 + HCI → MnCI2 + CI2 + H2O
State one characteristic of the chemical reaction which takes place when quicklime is treated with water
What do you understand by exothermic reactions?
Is Respiration an endothermic reaction or an exothermic reaction?
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.
An acid which can decolourise purple coloured potassium permanganate solution is:
(a) sulphuric acid
(b) citric acid
(c) carbonic acid
(d) hydrochloric acid
One of the following is an exothermic reaction. This is:
(a) electrolysis of water
(b) conversion of limestone into quicklime
(c) process of respiration
(d) process of photosynthesis
When water is added gradually to a white solid X, a hissing sound is heard and a lot of heat is produced forming a product Y. A suspension of Y in water is applied to the walls of a house during white washing. A clear solution of Y is also used for testing carbon dioxide gas in the laboratory.
(a) What could be solid X? Write its chemical formula.
(b) What could be product Y? Write its chemical formula.
(c) What is the common name of the solution of Y which is used for testing carbon dioxide gas?
(d) Write chemical equation of the reaction which takes place on adding water to slid X.
(e) Which characteristic of chemical reactions is illustrated by this example?
The removal of oxygen from a substance is called:
(a) oxidation
(b) corrosion
(c) reduction
(d) rancidity
Name the type of chemical reaction shown by the following equation:
2Mg+ O2 → 2MgO
Write your observation for the following chemical reaction and name the product formed :
When water is added to quick lime?
Balance the following equation. Also name the products formed.
`"Mg" + "O"_2 → "MgO"`
Balance the following equation. Also name the product formed.
` "H"_2"O"_2 → "H" _2 "O" + "O"_2`
In the experiment for determining the percentage of water absorbed by raisins, we do the final weighing of the raisins after keeping them dipped in water for about one hour. For the accuracy of the result, the extra water from the surface of the soaked raisins is removed by
What do the following symbol stand for?
2H2
What is the limitation of the reaction given in question 2?
Write the chemical equation for the following word equation and balance them.
Nitrogen + Oxygen → Nitrogen monoxide
Write the balanced chemical equation of the following reaction. potassium bicarbonate + sulphuric acid → potassium sulphate + carbon dioxide + water
Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Zinc reacts with silver nitrate to produce zinc nitrate and silver.
Answer the following question:
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.
Write word equation for the following molecular equation:
\[\ce{CaCO3 + 2HCl ->[\triangle] CaCl2 + H2O + CO2 [g]}\]
Word equation:
State which characteristic does [g] in the above reaction indicate. The word equation of:
In certain reaction an insoluble solid called precipitate is formed. State the colour and name of the precipitate formed in the following reaction involving addition of:
Lead nitrate to ammonium hydroxide.?
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Heat energy
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Light energy
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Electrical energy
Balance the following simple equation:
C + O2 → CO
Balance the following simple equation:
ZnS + O2 → ZnO + SO2
Balance the following simple equation:
H2S + Cl2 → S + HCl
Balance the following simple equation:
\[\ce{Ca(OH)2 + HNO3 -> Ca(NO3)2 + H2O}\]
Write a balanced equation for the following word equation:
Aluminium + Oxygen → Aluminium oxide
Write a balanced equation for the following word equation:
Potassium bicarbonate → Potassium carbonate + Water + Carbon dioxide
Give a balanced equation by partial equation method, [steps are given below].
The reaction of excess ammonia with chlorine – Ammonia as a reducing agent
- Ammonia first reacts with chlorine to give hydrogen chloride and nitrogen.
- Hydrogen chloride then further reacts with excess ammonia to give ammonium chloride.
Balance the following chemical equation.
- Na + O2 → Na2O3
- Ca + N2 → Ca3N2
- N2 + H2 →NH3
- CaCO3 +HCl → CaCl2 + CO2 +H2O
- Pb(NO3)2 → PbO + NO2 + O2
Which of the following statements about the given reaction are correct?
`3"Fe"("s") + 4"H"_2"O"("g") -> "Fe"_3"O"_4("s") + 4"H"_2("g")`
- Iron metal is getting oxidised
- Water is getting reduced
- Water is acting as reducing agent
- Water is acting as oxidising agent
What is a reactant in a chemical equation?
What is a product in a chemical equation?
A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution.
- Write the name of the compound formed and its colour.
- Write a balanced chemical equation for the reaction involved.
