Answer:
a) formula for citric acid is - C6 H8 o7
b) lime water turns opaque after adding co2 due to the formation of calcium carbonate.
c) reaction 3 is displacement reaction where a high reactive metal displace a less reactive from its salt solution.
d) reaction 1) is combination reaction where two reactant combines to give a single product whereas reaction 2) is decomposition reaction where a single reactant splits into more that 1 products.