Category: Chemical Engineering Math
"Published in Newark, California, USA"
What is the pH of the resulting solution made by mixing 25 mL of 0.1 M HCl and 15 mL of 0.1 M NaOH?
Solution:
The given word problem is about the mixing of an acid and a base. If you mix an acid and a base, their products are salt and water. The chemical reaction for the given mixture is written as follows
In order to convert the HCl and NaOH completely into NaCl and water, you must have equal moles at each reactants which are HCl and NaOH. Let's see if the two reactants will be used completely as follows
Since the number of moles of HCl is greater than the number of moles of NaOH, then the resulting solution is an acid.
Hence, the molarity of the resulting solution which is HCl is
Since HCl is a strong acid, then it is completely ionized as follows
Therefore, the pH of the resulting solution which is HCl solution is
Category: Chemical Engineering Math
"Published in Newark, California, USA"
Calculate the pH of 3.5 x 10-3 M HNO3.
Solution:
Let's consider the ionization of HNO3 as follows
Since HNO3 is a strong acid, then it is ionized completely into H+ and NO3-.
Therefore, the pH of a given solution is
Category: Chemical Engineering Math
"Published in Newark, California, USA"
A 250 mg sample containing 45% MgCO3 and 55% CaCO3 was ignited producing CO2 as decomposition product. Assuming that the decomposition reaction is complete, what is the change in weight of a NaOH solution used to absorb CO2?
Solution:
From the description of a given problem, it is about decomposition reaction. The mixture of MgCO3 and CaCO3 is decomposed by heat as follows
and then NaOH solution is used to absorb CO2 as follows
By gravimetric analysis, the weight of CO2 from MgCO3 is
By gravimetric analysis, the weight of CO2 from CaCO3 is
Therefore, the change of weight of a NaOH solution used to absorb CO2 which is also equal to the total weight of CO2 is
