Experiment 36 Acid Base Titrations 1, Lab Report Example

Standard Solution

A standard solution is a solution which possesses a precise known concentration. In the e valuation of acids and bases whose composition is unknown, there is a requisite of having a standard solution in order to catalyse a reaction with the substances which have unknown characteristics (Ophardt 1; Rushin 1).

Neutralization

This occurs when the acidic and caustic qualities of a substance are eradicated by the conversion of the hydronium (H⁺) and the hydroxide ions (OH^–) in order to create water as a by-product. There is a double replacement reaction that takes place in neutralization. The other by product is usually a salt residue (Ophardt 1; Rushin 1).

Titrant

The titrant facilitates the determination of the saturation of the acids and the bases to be ascertained with an elevated level of precision. The titrant is usually the main standard of assessment. The titrant should have an elevated level of purity. In addition, the titrant should have characteristics which enable it to remain stable when in contact with the air and during storage. Furthermore, the titrant must have the quality of an elevated level of molar weight in order to diminish the massing errors. Finally, the titrant must have the capacity of reacting with the standard solution in a concise a pre-determined manner (Ophardt 1; Rushin 1).

Potassium Hydrogen Phthalate

Potassium hydrogen phthalate is a molecule which has the qualities of a titrant. This infers that it has an elevated molecular mass. The potassium hydrogen phthalate molecule is delineated as KHC₈H₄O₄ which has a molar weight of 204.2 g/ mol.  The entire formula is usually not written, it is abbreviated as KHP where the P represents the phthalate ion. The phthalate ion is written as C₈H₄O₄^2-. The P for phthalate should not be confounded with the P which is the symbol for phosphorus (Ophardt 1; Rushin 1).

Acid Base Indicator

The acid base indicator is an expansive organic molecule which functions in a manner that is similar to a color dye. The acid base indicators have the quality of responding to the variation in the hydronium ion (H⁺). The most acid base indicator which was applied in the experiment is phenolphthalein. This is an acid bas indicator which is invisible in solution that have an acidic characteristic. The phenolphthalein converts to an acid base indicator which has a pink hue in the presence of the hydroxide (OH-) ions. . The hydroxide ions are normally encountered in solutions which have a pH that is more elevated that water (Ophardt 1; Rushin 1).

Suppose a sodium hydroxide solution was standardized against pure solid primary grade KHP (see question 1). If 0.4798 g of KHP required 45.22 mL of the sodium hydroxide to reach a phenolphthalein endpoint, what is the molarity of the NaOH solution?

The KHP molecule has a monoprotic characteristic and engages in a reaction with the NaOH molecule in a 1: 1 molar ratio. The equation is the following

KHC₈H₄O₄ (aq) + NaOH (aq) ? KNaC₈H₄O₄ + H₂O (l)

0.4798g / 202.4 g/ mole = 0.00237055336 moles of KHP (KHC₈H₄O₄). Consequently, taking into account that the KHP reacts with the NaOH in a 1: 1 molar ratio, the molar mass of the KHP is 0.00237055336 moles.

The solid acids chosen for the analysis were typically monoprotic acidic salts such as NaHSO₄ and KHSO₄, etc. Explain why such salts behave as strong enough acids to be titrable with NaOH using phenolphthalein as indicator.

The NaOH is a robust base and has the capacity of attracting the hydronium (H⁺) ions from the salts which are monoprotic (i.e., NaHSO₄ and KHSO₄). As the salts convert into becoming neutralize, there is small surplus of hydroxide ions (OH ^–). The small amount of the hydroxide (OH-) ions is sufficient to cause the phenolphthalein indicator to acquire a pink hue (Ophardt 1; Rushin 1).

Commercial vinegar is generally 5.0 ± 0.5% acetic acid by weight. Assuming this to be the true value for your unknown, how much were you in error by your analysis?

The amount of acetic acid by mass that was calculated was determined to be 4.41%. The percentage error is calculated by taking the empirical weight of acetic acid which is 5.0 while subtracting the laboratory value of the percentage mass of acetic acid. This amount is divided by the empirical mass of acetic acid in commercial vinegar. Consequently, the formula is the following:

(5.0- 4.41)/ 5.0 = .59/ 5.0 = 0.118

The percentage of error is 11.8% with regards to the laboratory values of the mass of acetic acid (Ophardt 1; Rushin 1).

Use a chemical dictionary or encvclopedia to explain the difference between an indicator endpoint for a titration analysis and the true equivalence point for the titration.

The point of equivalence is when the correct quantity of acid has been aggregated to the base. The end point is when the indicator changes in its hue. In the event that the point where the indicator changes is not precisely the same point to the pH of the equivalence point, there can be an observable distinction with regards to the end point and the equivalence point (Ophardt 1; Rushin 1).

Works Cited

Ophardt, Charles E. “Acids and bases.” Virtual Chembook Elmhurst College, 2003. Web. 2 April 2015. http://www.elmhurst.edu/`Chm/vchembook/180acidsbases.html

Ophardt, Charles E. “Neutralization Reaction – Acids + Bases.”Virtual Chembook Elmhurst College, 2003. Web. 2 April 2015. http://www.elmhurst.edu/`Chm/vchembook/183neutral.html

Ophardt, Charles E. “Acids and base strength.” Virtual Chembook Elmhurst College, 2003. Web. 2 April 2015. http://www.elmhurst.edu/`Chm/vchembook/185strength.html

Ophardt, Charles E. “Indicators.” Virtual Chembook Elmhurst College, 2003. Web. 2 April 2015. http://www.elmhurst.edu/`Chm/vchembook/186indicator.html

Ophardt, Charles E. “pH scale.” Virtual Chembook Elmhurst College, 2003. Web. 2 April 2015. http://www.elmhurst.edu/`Chm/vchembook/184ph.html

Rushin, W.G.”Chemical analysis by acid- base titration.” Cary Academy, 2015. Web. 2 April 2015. http://chem.lapeer.org/Chem2Docs/AcidBasetitration.html