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प्रश्न
Grills of doors and windows are always painted before they are used.
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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
How will you indicate the following effect in a chemical equation?
A solution made in water.
Balance the following equations:
\[\ce{Al(OH)3 -> Al2O3 + H2O}\]
Chemical equations are balanced to satisfy the law of ______.
A solution made in water is known as an ______ solution and indicated by the symbol ______.
What is a chemical equation? Explain with the help of an example.
Balance the following chemical equation:
\[\ce{NH3 -> N2 + H2}\]
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.”
State one characteristic of the chemical reaction which takes place when wax is burned in the form of a candle.
You are given the solution of lead nitrate. In order to obtain a yellow precipitate you should mix with it a solution of ______.
The chemical equations are balanced to satisfy one of the following laws in chemical reactions. This law is known as:
Balance the following chemical equation:
\[\ce{Pb(NO3)2_{(s)} ->[Heat] PbO_{(s)} + NO2_{(g)} + O2_{(g)}}\]
Write word equation for the following skeletal equation:
\[\ce{FeCl2 + Cl2 -> FeCl3}\]
Write your observation for the following chemical reaction and name the product formed :
When an aqueous solution of sodium chloride is mixed with an aqueous solution of silver nitrate.
Balance the following equation. Also name the product formed.
`"NaNO"_3 → "NaNO"_2 + "O"_2` Name of product (s)
Balance the following equation. Also name the products formed.
\[\ce{Ag + S -> Ag2S}\]
Balance the following equation. Also name the product formed.
K2O + H2O → KOH
Balance the following equation. Also name the product formed.
CO2 + C → CO
Balance the following equation. Also name the product formed.
N2 + H2 → NH3
While performing the experiment with raisins to determine the percentage of water absorbed by them, a student made following measurements:
Mass of water in the beaker = 40 g
Mass of raisins before soaking = 5 g
Mass of raisins after soaking for 2 hours = 8 g
Mass of water left in the beaker after the experiment = 35 g
The percentage of water absorbed by raisins is:
Balance the equation stepwise.
H2S2O7(l) + H2O(l) → H2SO4(l)
Balance the equation stepwise.
Ag(s) + HCl(aq) → AgCl ↓+ H2 ↑
Balance the equation stepwise.
NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + H2O(l)
Show the formation of Na2O by the transfer of electrons.
Write the balanced chemical equation of the following reaction. sodium hydroxide + sulphuric acid → sodium sulphate + water
Write the balanced chemical equations of the following reactions.
chlorine + sulphur dioxide + water → sulphuric acid + hydrogen chloride
Write the balanced chemical equation of the following reaction.
aluminium + sodium hydroxide + water → sodium meta aluminate + hydrogen
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate moles of chlorine gas formed.
Name the substance that is getting oxidised in the thermit process.
Write word equation for the following molecular equation:
CaO + H20 → Ca (OH)2 + Δ
Word equation:
State why [+ Δ ] is not written in the reaction, if ZnO reacts with H2O.
A chemical reaction is generally accompanied by certain external indications or characteristics. These include – change of – (a) colour (b) state (c) smell (d) evolution of gas (e) formation of precipitate (f) evolution or absorption of heat. With reference to change of colour – state the change in colour seen when the following are heated – lead [IV] oxide.
In certain reaction a change of state is observed i.e. solid to liquid, liquid to gas etc. – State the change of state of the products – to give the respective reactant.
2H2 + O2 → 2H2O
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Pressure
Give an example of a chemical equation in which two reactants form:
four product
Balance the following simple equation:
Ca + H2O → Ca(OH)2 + H2
Balance the following simple equation:
Fe + H2O ⇌ Fe3O4 + H2
Underline the compound in the equation given below, it is incorrectly balanced and write the correct balancing for the same.
Fe2O3 + 2H2 → 2Fe + 3H2O
Underline the compound in the equation given below, it is incorrectly balanced and write the correct balancing for the same.
NaOH + CO2 → Na2CO3 + H2O
Balance the given chemical reaction as per the instructions below.
\[\ce{NaOH + H2SO4 -> Na2SO4 + H2O}\]
Make a list of the elements in the chemical equation.
To balance the following chemical equation the value of x and y should respectively be:
\[\ce{2NaOH + xAl_2O_3->yNaAlO_2 + H_2O}\]
When aqueous solutions of potassium iodide and lead nitrate are mixed an insoluble substance separates out. The chemical equation for the reaction involved is:
