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प्रश्न
What is a chemical reaction?
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उत्तर
“Chemical reaction is a chemical change in which matter changes into a new substance or substances.”
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Iron pipes coated with zinc do not get rusted easily.
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Compounds, which in their molten state allow an electric current to pass through them are called
- electrolytes
- non-electrolytes
- non-conductors
- none of these
Write true or false :
When potassium iodide solution is added to lead acetate solution a red precipitate is formed.
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)
Electron ______ is complete in each hydrogen in a hydrogen molecule.
Write the chemical reaction where the following changes are observed.
Colour change is noticed
Multiple choice:
Thermal decomposition of sodium carbonate will produce
Name: A brown gas
Give a chemical test to distinguish between the following gases.
H2 and CO2
What do you observe when dilute sulphuric acid is added to the following:
Sodium Sulphide
Distinguish by heating the following in dry test tubs.
Zinc nitrate and copper nitrate.
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
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 ammonium dichromate | Name of neutral gas evolved |
Complete the table given below.
| Flame test for calcium chloride | Acid used for flame test |
Give a balanced equation for the conversion of a soluble lead salt to an insoluble lead salt – formed as a white precipitate.
Higher order Thinking question
Peeled and unpeeled banana does not look the same. Does that mean peeling banana is a chemical change?
Chemists identify gypsum as a natural indicator.
On heating calcium carbonate gets converted into calcium oxide and carbon dioxide.
(a) Is this a physical or a chemical change?
(b) Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved.
Which of the following is/are true when milk changes into curd?
- Its state is changed from liquid to semi solid.
- It changes colour.
- It changes taste.
- The change cannot be reversed.
Choose the correct option from below:
A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.
What changes do you expect?
