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प्रश्न
How do the following help in bringing about a chemical change?
heat.
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उत्तर
Some chemical reactions take place only in the presence of heat.
e.g. When lead nitrate is heated, it breaks into lead monoxide, nitrogen dioxide and oxygen.
\[\ce{\underset{\text{(lead nitrate)}}{2Pb(NO3)2}->[heat]\underset{\text{lead monoxide}}{2PbO} +\underset{\text{nitrogen dioxide}}{4NO2} + O2}\]
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संबंधित प्रश्न
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer
Which of the following is a reducing agent?
- oxygen
- chlorine
- hydrogen
- none of these
Differentiate between in Chemical reaction and chemical equation.
Complete the statement by filling the gaps using appropriate term from the terms given in the bracket.
(slow, coloured, arrow, fast, smell, milky, physical, product, chemical, reactant, covalent, ionic, octet, duplet, exchange, sharing, equality sign)
Oxygen is a ______ in respiration.
Give an example of a reaction where the following are involved:
Close contact
Define a photochemical reaction.
Name: Gas with rotten egg smell.
State the original colour of the following substance and colour of residue obtained after heating.
Copper carbonate
Give a chemical test to distinguish between the following gases.
H2 and O2
Give a word equation for the following reaction.
A compound which on heating shows – colour change from brown to yellow.
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A white solid which evolves two colourless gases which on cooling combine and condense on the cooler parts of the test tube.
Complete the table given below.
| Heat on Zinc nitrate | Colour of residue |
State the following reaction represent oxidation or reduction.
\[\ce{Ag->Ag+}\]
A chemical reaction is often accompanied by external indications or characteristics.
Water boiling into water vapour is an example of chemical change.
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Do you think formation of rust from iron is a chemical change?
Match the following:
| Column I | Column II | ||
| 1. | Burning of coal | a. | Rusting |
| 2. | Painting of a surface | b. | Evaporation |
| 3. | Dipping iron in the water | c. | Chemical change |
| 4. | Salt from seawater | d. | Prevention of rusting |
Write five changes in the characteristics of a substance that can take place during a chemical change.
When carbon dioxide is passed through lime water ______.
______ is the chemical name of slaked lime.
______ is the chemical name of limestone.
