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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
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.
Correct and balance the following equation:
\[\ce{Ca + H2O -> CaOH + H}\]
Chemical equations are balanced to satisfy the law of ______.
State one characteristic of the chemical reaction which takes place when dilute hydrochloric acid is added to sodium carbonate.
What do you understand by endothermic reactions?
One of the following does not happen during a chemical reaction. This is:
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 will be formed if we add common salt solution to ______.
A colourless lead salt, when heated, produces a yellow residue and brown fumes.
- Name the lead salt.
- Name the brown fumes.
- Write a chemical equation of the reaction involved.
Write your observations and name the product when
Iron nails are added to an aqueous solution of copper sulphate.
Write word equation for the following skeletal equation:
\[\ce{KClO3 -> KCl + O2}\]
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.
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.
`"CO" + "O"_2 → " CO"_2`
Balance the following equation. Also name the product formed.
CO2 + C → CO
Balance the following equation. Also name the product formed.
N2 + H2 → NH3
Write your observation and name the product when zinc reacts with dilute hydrochloric acid.
Write your observation and name the product when ron nails are added to an aqueous solution of copper sulphate.
Explain the terms with examples.
Balanced equation
State the information conveyed by the following equation:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2 ↑
Write the balanced chemical equation of the following reaction.
aluminium + sodium hydroxide + water → sodium meta aluminate + hydrogen
Define: Endothermic reaction
Write word equation for the following molecular equation:
Na2SO3 + 2HCl [dil.] → 2NaCl + H2O + SO2 [g]
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.
\[\ce{2H2O ->[electric][current] 2H2 + O2}\]
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:
Iron [III] chloride to ammonium hydroxide.
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
Name the following:
A catalyst which increases the rate of a chemical reaction.
Give an example of a chemical equation in which two reactants form:
three product
Balance the following simple equation:
NO + O2 → NO2
Balance the following simple equation:
Fe + Cl2 → FeCl3
Balance the following simple equation:
Fe2O3 + H2 → Fe + H2O
Write a balanced equation for the following word equation:
Aluminium + Oxygen → Aluminium oxide
With reference to a chemical equation state which of the statements 1 to 5 pertain to A or B.
A: Information provided by a chemical equation.
B: Limitations of a chemical equation.
- The nature of the individual elements.
- The speed of the reaction.
- The state of matter in which the substance is present.
- The completion of the reaction.
- The direction of the reaction.
Write scientific reason.
Adding zinc particles to a solution of copper sulphate makes the blue solution colorless.
What is a chemical equation?
What is called thermolysis reactions?
Give the characteristic tests for the following gases :
- CO2
- SO2
- O2
- H2
Complete the following blank in the equation as indicated.
\[\ce{CaH2_{(s)} + 2H2O_{( aq)}-> Ca(OH)2_{(s)} + 2H2_{(g)}}\]
Molecules: 6.02 × 1023 + ______ `→` ______ + ______
