Question

Three samples of calcium carbonate are placed in the flasks for an investigation.
In flask E 5g of CaCO3 placed in large lumps.
In flask F 5g of CaCO3 placed in medium size lumps.
In flask G 5g of CaCO3 placed in small lumps.

The same volume, in excess,of dilute HCL is added to each flask. Loss of mass is determined in each flask with the help of electronic balances and graphs are plotted as shown in diagram.

I)the three flasks and their content lose mass due to the formation of?
a)O2. b)H2
c)CO2. d)CO

ii) how does rate of reaction change with time?
a) decreases with time
b) increase with time
c)does not change
d)first increases ,then decreases

iii)in which flask reaction is fastest
a) G b)E
c)F d)all have equal

iv)if we use powdered CaCO3 the reaction will be
a) faster. b) slower
c) moderate. d) equally in both cases

v) after how long reaction stops
a)80seconds
b)100 seconds
c)140 seconds
d)160 seconds
​​

Answer 1

Answer:

1)c)CO2

2)a)decrease with time

3)a)G

4)a)faster

Answer 2

Answer:

i) The three flasks and their content lose mass due to the formation of c)CO₂

• CO₂ gas is formed in the reaction which escapes and causes loss in mass.
• The reaction is CaCO₃(s) + 2HCl(dil) → CaCl₂(aq) + H₂O(l) + CO₂(g)

ii) The rate of reaction a)decreases with time.

• As the time increases, the concentration of the reactant CaCO₃ goes on decreasing.
• Hence, the rate of reaction also decreases.

iii) The reaction is faster in the a)G flask.

• Flask G has small lumps of CaCO₃.
• Small lumps react faster than large or medium-size lumps.
• It can also be seen from the graph that the G flask loses more mass in less time as compared to flasks E and F.

iv) If we use powdered CaCO₃, the reaction will be a)faster.

• The reaction will be faster than G because powdered CaCO₃ have more surface area.
• The rate of reaction increases as the surface area increases.

v) The reaction stops after b)100 seconds.

• As indicated in the graph, the mass in the G flask remains constant from t=100s.
• This means that by t=100s, as the reactant is used up and the reaction has stopped.

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