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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
Find the odd man out:
Turmeric, Methyl Orange, Rose petals, Beetroot.
Balance the following chemical equation:
\[\ce{NH3 -> N2 + H2}\]
One of the following is an exothermic reaction. This is:
Zinc oxide reacts with carbon, on heating, to form zinc metal and carbon monoxide. Write a balanced chemical equation for this reaction. Name
- oxidising agent, and
- reducing agent,
in this reaction.
Express the following facts in the form of a balanced chemical equation:
“When a strip of copper metal is placed in a solution of silver nitrate, metallic silver is precipitated and a solution containing copper nitrate is formed”.
Write a 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.
Write your observation and name the product when zinc reacts with dilute hydrochloric acid.
A student weighed some raisins and recorded the weight as ‘x’. She then soaked the raisins in distilled water. After about 2 hours she removed the raisins, wiped them dry and weighed them again, and recorded that as ‘y’. The percentage of water absorbed by raisins may be determined using the relationship.
Balance the equation stepwise.
H2S2O7(l) + H2O(l) → H2SO4(l)
Balance the following equation:
H2O + Cl2 → HCl + O2
Write the balanced chemical equation of the following reaction.
aluminium sulphate + sodium hydroxide → sodium sulphate + sodium meta aluminate + water.
Complete the following blank in the equation as indicated.
\[\ce{CaH2_{(s)} + 2H2O_{( aq)}-> Ca(OH)2_{(s)} + 2H2_{(g)}}\]
Moles: 1 mole + ______ `→` ______ + ______
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate the mass of acid required.
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.
Heat energy
Name the following:
The silvery residue obtained on heating mercury [II] oxide.
Name the following:
Two non-metal which react explosively when brought in close contact.
\[\ce{2KClO3->[MnO2] 2KCl + 3O2[g] - is a balanced equation.}\]
State why the compound MnO2 is written above the arrow.
Balance the following simple equation:
Al + H2O → Al2O3 + H2
Balance the following simple equation:
NaOH + Cl2 → NaCl + NaClO + H2O
