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प्रश्न
Grills of doors and windows are always painted before they are used.
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.
APPEARS IN
संबंधित प्रश्न
Translate the following statement into chemical equation and then balance it.
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Write the balanced chemical equation for the following reaction.
\[\ce{Aluminium + Copper chloride -> Aluminium chloride + Copper}\]
Complete and balance the following equation:
NaOH + ............ 
Na2 SO4 + H2O
Correct and balance the following equation:
Ca + H2O 
CaOH + H
Balance the given equation:
Mg(OH)2 + HCI MgCI + H2O
Balance the given equation:
NH3 + CuO 
Cu +N2 +H2O
Giving examples, state the difference between balanced and unbalanced chemical equations.
Balance the given chemical equation:
C + CO2 → CO
Balance the following equation and add state symbols:
Zn + HCI → ZnCI2 + H2
With the help of an appropriate example, justify that some of the chemical reactions are determined by Change in colour
Give chemical equation for the reaction involved in the above case.
Write balanced chemical equation with state symbols for the following reaction:
Barium chloride solution reacts with sodium sulphate solution to give insoluble barium sulphate and a solution of sodium chloride.
A white precipitate will be formed if we add common salt solution to:
(a) Ba(NO3)2 solution
(b) KNO3 solution
(c) AgNO3 solution
(d) Mg(NO3)2 solution
Name the type of chemical reaction shown by the following equation:
2Mg+ O2 → 2MgO
Write word equation for the following skeletal equation:
\[\ce{AgBr -> Ag + Br2}\]
Balance the following chemical equation :
Na20 + H20 → NaOH
Write symbolic representation for the following word equation and balance them :
Calcium carbonate → Calcium oxide + Carbon dioxide.
Balance the following equation :
Pb3O4 → PbO + O2
Balance the following equation. Also name the products formed.
\[\ce{Ag + S -> Ag2S}\]
Balance the following equation. Also name the product formed.
CO2 + C → CO
In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?
Balance the equation stepwise.
SO2(g) + H2S(aq) → S(s) + H2O(l)
Write the chemical equation for the following word equation and balance them.
Magnesium + Sulphuric acid → Magnesium sulphate + Hydrogen
Balance the following equation:
Pb3O4 → PbO + O2
Considering the relationship in the first pair, complete the second paie :
AgCI : White :: CuI2 : ___________
What is thermit process? Where is this process used? Write a balanced chemical equation for the reaction involved.
Write word equation for the following molecular equation:
\[\ce{NH3 [g] + HCl [g] ⇌ NH4Cl [s]}\]
Word equation:
State which characteristic is observed in the above reaction.
Give an-example of a similar above characteristic, seen between two other gaseous reactants.
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 – copper carbonate.
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 [II] sulphate to sodium 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:
Copper [II] sulphate to sodium hydroxide.
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Electrical energy
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Catalyst
Representation of the results of a chemical change – is a chemical equation.
For the equation: FeCl3 + 3NH4OH 3NH4Cl + Fe(OH)3 ↓
Answer the following:
What is the indications of the arrow between the reactants and the products and of the arrow pointing downwards at the end.
Give word equation for the following chemical reaction and give the names of the product formed.
Zn + 2HC1→ ZnCl2 + H2
Give reason for the following:
Silver salts are kept in dark coloured bottles.
Give an example of a chemical equation in which two reactants form:
three product
Balance the following simple equation:
H2S + Cl2 → S + HCl
Balance the following simple equation:
Fe2O3 + CO → Fe + CO2
Write a balanced equation for the following word equation:
Potassium bicarbonate → Potassium carbonate + Water + Carbon dioxide
Which of the following is not a physical change?
The following reaction is an example of a `4"NH"_3("g") + "SO"_2 -> 4"NO"("g") + 6"H"_2"O"("g")`
- displacement reaction
- combination reaction
- redox reaction
- neutralisation reaction
