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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
Translate the following statement into chemical equation and then balance it.
Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.
2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.
Find the odd man out:
Turmeric, Methyl Orange, Rose petals, Beetroot.
State whether the following statement is true or false:
A chemical equation can be balanced easily by altering the formula of a reactant or product.
Balance the given chemical equation:
NH3 → N2 + H2
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 non-metals.
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.
Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for this reaction and indicate the evolution of gas.
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?
When a mixture of gases X and Y is compressed to 300 atm pressure and then passed over a catalyst consisting of a mixture of zinc oxide and chromium oxide (heated to a temperature of 300°C), then an organic compounds Z having the molecular formula CH4O is formed. X is a highly poisonous gas which is formed in appreciable amounts when a fuel burns in a limited supply of air; Y is a gas which can be made by the action of a dilute acid on an active metal; and Z is a liquid organic compound which can react with sodium metal to produce hydrogen gas.
(a) What are X, Y and Z?
(b) Write a balanced chemical equation of the reaction which takes place when X and Y combine to form Z. Indicate the conditions under which the reaction occurs.
Balance the following chemical equation:
The removal of oxygen from a substance is called:
(a) oxidation
(b) corrosion
(c) reduction
(d) rancidity
Write word equation for the following skeletal equation:
\[\ce{KClO3 -> KCl + O2}\]
Write word equation for the following skeletal equation:
\[\ce{Na + O2 -> Na2O}\]
Write your observation for the following chemical reaction and name the product formed :
When dilute acetic acid is poured on baking soda.
Write your observation for the following chemical reaction and name the product formed :
When ammonium chloride is heated with sodium hydroxide.
Balance the following equation. Also name the product formed.
N2 + H2 → NH3
State the information conveyed by the following equation:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2 ↑
Balance the following equation:
Fe + H2O → Fe3O4 + H2
Balance the following equation:
Pb3O4 → PbO + O2
Balance the following equation:
NO2 +H2O → HNO2 + HNO3
Write the balanced chemical equation of the following reaction. sodium hydroxide + sulphuric acid → sodium sulphate + water
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.
ammonia + oxygen → nitric oxide + water
How is a flame test performed?
Name the substances that are getting oxidised and reduced in the process.
When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.
Write the balanced chemical equation for this reaction.
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:
Write word equation for the following molecular equation:
\[\ce{H2 [g] + Cl2 [g] ->[sunlight] 2HCl}\]
Word equation:
State which form of energy is utilised in the above chemical reaction.
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.
\[\ce{C +2S -> CS2}\]
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Catalyst
Give word equation for the following chemical reaction and give the names of the product formed.
Zn + S → ZnS
Give word equation for the following chemical reaction and give the names of the product formed.
NH3 + HCl→ NH4Cl
Name the following:
The silvery residue obtained on heating mercury [II] oxide.
Name the following:
A catalyst which increases the rate of a chemical reaction.
Write word equation for the following chemical reaction given below. Also state the observation seen in the case.
\[\ce{ZnCo3->[\triangle] ZnO + CO2}\]
\[\ce{2KClO3->[MnO2] 2KCl + 3O2[g] - is a balanced equation.}\]
State what is a ‘balanced equation’.
Balance the following simple equation:
K + CO2 → K2O + 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.
NaOH + CO2 → Na2CO3 + H2O
