How does dissolved CO2 in distilled water affect the accuracy of the determination of a NaOH solution's concentration? How is the term acid anhydride applied here?
I know you had answered this already, but what if KHP is used to titrate the NaOH. In this experiment KHP was used to standardize NaOH.
I tried to find the response I made to your earlier question but I can't find it. At any rate, it doesn't matter what is used to standardize the NaOH. What is important is how many of the H atoms of the H2CO3 formed you titrate. That depends upon what kind of indicator you use. With methyl red indicator both of the H atoms are titrated so there is no error. With phenolphthalein indicator (which is used for KHP vs NaOH) only one H of H2CO3 is titrated and there US an error. The molarity of NaOH will be too high (meaning that the concn NaOH actually is lower than you have calculated.) By the way, this has a name; it is called "carbonate error".
When dissolved CO2 is present in distilled water, it can react with NaOH to form sodium carbonate (Na2CO3) and water. This reaction can lead to an inaccurate determination of the NaOH solution's concentration because the CO2 consumption may be erroneously attributed to the NaOH concentration.
In the context of acid anhydride, it refers to CO2 acting as an anhydrous acid in the presence of water. Anhydrous acids are substances that can release H+ ions when dissolved in water, and CO2 can behave as an acid under certain conditions.
Now, if KHP (potassium hydrogen phthalate - C8H5KO4) is used to titrate the NaOH solution, the effect of dissolved CO2 can still affect the accuracy of the determination. During the titration, NaOH reacts with KHP to form water and potassium salt of phthalic acid. However, any dissolved CO2 could react with NaOH instead of KHP, leading to an underestimation of the NaOH concentration. This would result in a lower calculated concentration of NaOH based on the volume of KHP used, and therefore an inaccurate standardization of the NaOH solution using KHP as the titrant.
To minimize the impact of dissolved CO2, a sodium carbonate solution (Na2CO3) can be titrated with the NaOH solution to determine the exact concentration of NaOH. By subtracting the volume of NaOH used in the titration with Na2CO3 from the total volume of NaOH required in the KHP titration, the effect of dissolved CO2 can be accounted for.
When dissolved CO2 is present in distilled water, it can react with the NaOH solution to form carbonic acid (H2CO3), which can then react with the NaOH as well. This reaction between the dissolved CO2 and NaOH can lead to inaccurate determination of the NaOH solution's concentration because it consumes some of the NaOH that is intended to react with the KHP during titration.
Now, let's discuss the term "acid anhydride" in this context. An acid anhydride is a compound that can react with water to form an acid. In the case of CO2, it can be considered an acid anhydride because it reacts with water to form carbonic acid (H2CO3). Therefore, CO2 dissolved in water can be referred to as an acid anhydride.
Now, if KHP is used to titrate the NaOH solution, it is important to factor in the effect of dissolved CO2 because it can still react with the NaOH. However, in this experiment, KHP is used to standardize NaOH. This means that the concentration of NaOH is determined using the known concentration of KHP. The presence of dissolved CO2 in the distilled water during standardization might affect the accuracy of the NaOH concentration determination, but it would not directly affect the titration process between KHP and NaOH.