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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.
Translate the following statement into a chemical equation and then balance the equation:
Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
Balance the following equations:
\[\ce{Al(OH)3 -> Al2O3 + H2O}\]
Rewrite the following information in the form of a balanced chemical equation:
Magnesium burns in carbon dioxide to form magnesium oxide and carbon.
With the help of an appropriate example, justify that some of the chemical reactions are determined by a change in colour.
Give a chemical equation for the reaction involved in the above case.
What do you understand by exothermic reactions?
Which of the following does not involve a chemical reaction?
The chemical reaction between two substances is characterised by a change in colour from orange to green. These two substances are most likely to be ______.
The chemical reaction between quicklime and water is characterised by ______.
When metal X is treated with a dilute acid Y, then a gas Z is evolved which burns readily by making a little explosion.
- Name any two metals which can behave like metal X.
- Name any two acids which can behave like acid Y.
- Name the gas Z.
- Is the gas Z lighter than or heavier than air?
- Is the reaction between metal X and dilute acid Y exothermic or endothermic?
- By taking a specific example of metal X and dilute acid Y, write a balanced chemical equation for the reaction which takes place. Also indicate physical states of all the reactants and products.
A white precipitate can be obtained by adding dilute sulphuric acid to ______.
Name the type of chemical reaction shown by the following equation:
2Mg+ O2 → 2MgO
Write symbolic representation for the following word equation and balance them :
Calcium carbonate → Calcium oxide + Carbon dioxide.
Balance the following equation Also name the product formed.
`"K" + "CI"_2 → "KCI"`
Balance the following equation. Also name the product formed.
FeCI2 + CI2 → FeCI3
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:
In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?
Explain the terms with examples.
Balanced equation
Balance the equation stepwise.
H2S2O7(l) + H2O(l) → H2SO4(l)
Show the formation of Na2O by the transfer of electrons.
Write the chemical equation for the following word equation and balance them.
Sodium reacts with water to form sodium hydroxide and hydrogen
Balance the following equation:
Zn + KOH → K2ZnO2 + H2
Balance the following equation:
Pb3O4 → PbO + O2
Write the balanced chemical equation of the following reaction.
aluminium sulphate + sodium hydroxide → sodium sulphate + sodium meta aluminate + water.
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate mass of MnO2 used.
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate the mass of acid required.
Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.
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 – zinc carbonate.
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Electrical energy
Representation of the results of a chemical change – is a chemical equation.
For the equation: FeCl3 + 3NH4OH 3NH4Cl + Fe(OH)3 ↓
Answer the following:
Write the word equation for the above molecular equation.
Representation of the results of a chemical change – is a chemical equation.
For the equation: FeCl3 + 3NH4OH 3NH4Cl + Fe(OH)3 ↓
Answer the following:
Is the equation given above a balanced equation. Give reasons.
Give reason for the following:
Silver salts are kept in dark coloured bottles.
Balance the following simple equation:
NaHCO3 + H2SO4 → Na2SO4 + H2O + CO2
Write a balanced equation for the following word equation:
Iron + Hydrochloric acid → Iron [II] chloride + Hydrogen
What is called thermolysis reactions?
Which among the following is(are) double displacement reaction(s)?
- `"Pb" + "CuCl"_2 -> "PbCl"_2 + "Cu"`
- `"Na"_2"SO"_4 + "BaCl"_2 -> "BaSO"_4 + 2"NaCl"`
- `"C" + "O"_2 -> "CO"_2`
- `"CH"_4 + 2"O"_2 -> "CO"_2 + 2"H"_2"O"`
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.
Dil. HCl is added to Zn granules. How will you prove that chemical change has taken place here? Support your response with two arguments.
