Cathode Ray experiment to figure out electrons exist -> atoms can be broken up into subatomic particles
Percent error (%)= 
Accepted value is true value.
Measured values is calculated value.
In the question given Accepted value (true value) = 63.2 cm
Given Measured(calculated values) = 63.1 cm , 63.0 cm , 63.7 cm
1) Percent error (%) for first measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.1 cm
Percent error (%)= 



Percent error = 0.158 %
2) Percent error (%) for second measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.0 cm
Percent error (%)= 



Percent error = 0.316 %
3) Percent error (%) for third measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.7 cm
Percent error (%)= 




Percent error = 0.791 %
Percent error for each measurement is :
63.1 cm = 0.158%
63.0 cm = 0.316%
63.7 cm = 0.791%
Answer:
MgCl₂+ Na₂CO₃ ==> MgCO₃ + NaCl
From a quick observation
You see that the right hand side of the eqn is deficient of Sodium and Chlorine
Simply Add a Coefficient of 2 to NaCl to balance it with the left.
Your answer now becomes
MgCl₂ + Na₂CO₃ ==> MgCO₃ + 2NaCl.✅