Question

When magnesium burns in air a white powder of magnesium oxide is formed, Write a
chemical equation for the reaction.
Q.2 Balance the following equations
i. Na + H2O → NaOH + H2
ii. NaHCO3 → Na2CO3 + H2 O + CO2
iii. NH3 + Cl2 → NH4Cl + N2
Q.3 Fill in the blanks from the words given alongside
i. Formation of a new substance is a_________ change. ( physical/chemical)
ii. A shorthand notation of a chemical reaction is called a chemical _______.
(equation /symbol)
iii. In a chemical reaction the atoms of elements are________.
(gained/lost/conserved)
iv. In the equation given below, the value of X is________. (4/6)
2 Pb(NO3)2 → 2PbO + X NO2 + O2
Q.4 Given below are word equations. Write chemical equations for them.
i. Mercury reacts with chlorine to form mercuric chloride.
ii. On heating zinc carbonate evolves carbon dioxide and forms a residue of zinc oxide.
iii. Iron filings and sulphur undergo a chemical change to form ferrous sulphide.
iv. On heating blue crystals of copper sulphate a white amorphous powder is formed.
v. Nitrogen and hydrogen react to form ammonia.
Q.5

Write the chemical equations of the reaction in which the following changes have
taken place with an example of each:
i. Change in colour
ii. Change in temperature
iii. Formation of precipitate

Answer 1

Q3.i)chemical

ii.equation

iii.conserve

Answer 2

Explanation:

Q1)

the equation will be

magnesium + oxygen ------ magnesium oxide