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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?
Endothermic reaction
Translate the following statement into a chemical equation and then balance the equation:
Aluminium metal replaces iron from ferric oxide, Fe2O3, giving aluminium oxide and iron.
Write the balanced equation for the following reaction, and add the state symbol:
Sodium hydroxide reacts with sulphuric acid to produce sodium sulphate and water.
Carbon monoxide reacts with hydrogen under certain conditions to form methanol (CH3OH). Write a balanced chemical equation for this reaction indicating the physical states of reactants and product as well as the conditions under which this reaction takes place.
With the help of an appropriate example, justify that some of the chemical reactions are determined by the evolution of a gas.
Give a chemical equation for the reaction involved in the above case.
With the help of an appropriate example, justify that some of the chemical reactions are determined by a change in temperature.
Give a chemical equation for the reaction involved in the above case.
Give one example of a chemical reaction characterised by a change in state.
The chemical reaction between quicklime and water is characterised by ______.
Which of the following is not an endothermic reaction?
Balance the following chemical equation:
\[\ce{Pb(NO3)2_{(s)} ->[Heat] PbO_{(s)} + NO2_{(g)} + O2_{(g)}}\]
What happens when silver nitrate solution is added to sodium chloride solution?
- Write the equation for the reaction which takes place.
- Name the type of reaction involved.
Write word equation for the following skeletal equation:
\[\ce{Na + O2 -> Na2O}\]
Balance the following equation. Also name the product formed.
`"H"_2 +"CI"_2 → "HCI"`
Balance the following equation. Also name the product formed.
`"Zn" + "HCI" → "ZnCI" _2 + "H"_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
Balance the equation stepwise.
Ag(s) + HCl(aq) → AgCl ↓+ H2 ↑
Write the answer to the following.
Explain the similarity in two events, namely adding NaOH to water and adding CaO to water.
Sodium chloride reacts with silver nitrate to produce silver chloride and sodium nitrate
Write the equation.
Check whether it is balanced, if not balance it.
Find the weights of reactants and products.
State the law which this equation satisfies.
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.
iron pyrites(FeS2) + oxygen → ferric oxide + sulphur dioxide
Write the balanced chemical equation of the following reaction.
Potassium permanganate + hydrochloric acid → potassium chloride + manganese chloride + chlorine + water
Write the balanced chemical equation of the following reaction.
potassium dichromate + sulphuric acid → potassium sulphate + chromium sulphate + water + oxygen.
Write the balanced chemical equation of the following reaction.
potassium dichromate + hydrochloric acid → Potassium chloride + chromium chloride + water + chlorine
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.
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.
\[\ce{2H2O ->[electric][current] 2H2 + O2}\]
Give reason for the following:
Silver salts are kept in dark coloured bottles.
Write word equation for the following chemical reaction given below. Also state the observation seen in the case.
\[\ce{Na2SO3 + 2HCl ->[\triangle] 2NaCl + H2O + SO2}\]
\[\ce{2KClO3->[MnO2] 2KCl + 3O2[g] - is a balanced equation.}\]
Give a reason why the above equation is balanced.
Balance the following simple equation:
SO2 + O2 ⇌ SO3
Balance the following simple equation:
NaHCO3 + H2SO4 → Na2SO4 + H2O + CO2
Balance the following simple equation:
Mg + CO2 → MgO + C
Underline the compound in the equation given below, it is incorrectly balanced and write the correct balancing for the same.
Na2SO3 + HCl → 2NaCl + H2O + SO2
Underline the compound in the equation given below, it is incorrectly balanced and write the correct balancing for the same.
3CuO + NH3 → 3Cu + 3H2O + N2
Write scientific reason.
Adding zinc particles to a solution of copper sulphate makes the blue solution colorless.
A dilute ferrous sulphate solution is gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?
Give the characteristic tests for the following gases :
- CO2
- SO2
- O2
- H2
To balance the following chemical equation the value of x and y should respectively be:
\[\ce{2NaOH + xAl_2O_3->yNaAlO_2 + H_2O}\]
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.
