How many moles of CO2 are present in the flask after 4mL of HCl have been added? What is the stoichiometric ratio between HCl adn CO2?

Question

Flask is 150mL. P=1.81atm. Gas volume=135.9ml. Liquid volume=14.1mL.  I need help with putting this into an equation and writing the balanced equation for sodium bicarbonate and HCl.

Answer 1

The Stoichiometric balanced equation is

 

NaHCO3 + HCl ==>  CO2 + NaCL + H2O

 

Thus the molar ratios are all 1:1

 

The initial pressure in the flask was not specified, nor was the Kelvin temperature.   However, assuming that the initial pressure was one atm, the the temperature was 293K,  the idea gas equation can be used to figure the number of moles of CO2 needed to get a partial pressure of 0.81 atm.   The result is 0.00458 moles of CO2.   Since the molar ratios are 

1:1, this means that 0.00458 moles of HCl were added (assuming that HCl was limiting).   Since the volume of HCl was 0.004 L,  this implies that the molarity of the added acid was .00458/.004 = 1.145 .   This is a pretty reasonable value. 

 

Of course a different temperature and/or a different starting pressure would lead to different numbers.