Hibiscus Acid Base Indicator Experiment, Essay Example

Introduction

The application of hibiscus sabdariffa leafs as a component of a natural acid base indicator was reviewed. The hibiscus flower is composed of anthocyanin pigment. The anthocyanin pigment has a color that is dependent on the pH value. The equilibrium of the acids- base responses pertaining to the hibiscus pigment had been reviewed. The values of the pK_a had been encountered to be 3.0 and 7.5 (Yakasai 62).

Research Question

The research question is: What is the optimal temperature for the mechanism by which the pigments in the hibiscus sabdariffa  effectively serve as an acid- base indicator in titration?

Variables

The dependent variable is the color of the indicator as an acid base titration due to the concentration of the hydrogen ions. This is the variable being manipulated which responds. The manner by which the responding variable can be manipulated is to add a more robust acid or base to the solution that falls within the range of measurement of the values of the pK_awhich had been encountered to be 3.0 and 7.5 (Yakasai 62). The independent variable is the pH. The concentration of hydronium ions in a solution being assessed is the constant.

Background

Hibiscus sabdariffa is an herb that has a perennial quality that reaches a height of 2.5 meters. The economic applications of the plant are commonly found as potherbs and garden ornamentals. These plants are used regionally in Africa and Asia. The hibiscus is applied as a dying agent in additional to a medicinal herb. The extract of hibiscus is consumed in Africa as a hot or cold beverage (Yakasai 62).

The hibiscus is designated as people of Gambia designate the drink wonjo, as karkaday in Egypt, zobo in Nigeria, and omutete in Namibia (Yakasai 62).  Research has demonstrated that the enhanced formation of the reactive oxygen and free radicals have been demonstrated as contributors to cardiovascular disease. Hibiscus sabdariffa has been demonstrated to be an antioxidant which reduces the potential for cardiovascular disease (Oshana & D’Mello 276).

Materials and Experimental Procedure

Materials

• Ten hibiscus flowers.
• Ethyl Alcohol – 6 ml.
• Mortar and pestle.
• Container (200 ml).

Experimental Procedure

Take the ten hibiscus flowers and remove the stems. The petals should be the only components used in the experiment. Place the hibiscus petals in a container and add 6 ml of ethyl alcohol. Remove the petals from the container and place them into a mortar and pestle. Apply the mortar in order to crush the flower petals. Remove the liquid as this will be applied as the acid – base indicator.

Results

In the event that acid solutions are aggregated to the liquid hibiscus extract, the color should become shades of red in accordance with the hydrogen concentration. In the event that a caustic is aggregated to the hibiscus extract solution, the color of the solution should migrate towards the ultraviolet – blue spectrum.

Discussion

The hibiscus flower is composed of anthocyanin which is a dye that is accountable for blue, violet, purple, red and pink hues in plants. The pigment that is derived modifies its color in accordance with the saturation of the hydrogen ions in the solution. Consequently, the dye found in the hibiscus can be applied as an acid base indicator in titration experiments. The formula that will be reviewed is the Henderson- Hasselbalch equation:

pKH_indicator  – log [H_ind] [Ind]^-1– log [VH_ind] [V_ind]^-1 = pH (UC Davis 1). 

Literature Review

Anthocyanins are some of the most significant collections of dyes that are water soluble. The anthocyanins are in the chemical category of flavonoids. These compounds are formulated on a C15 framework with a chromate disc that is composed of a secondary aromatic disc in the second position of the carbon chain. The anthocyanin has one of the sugar molecules that are linked by hydroxylases at distinct locations on the fundamental structure. The wide structural variation in the dyes of the anthocyanin category is attributed to the acylation and glycosylation of the Alcona moieties (Ben Amor & Allah 820; Braai 162).

The majority of the indicators that performed as acid- base demonstrators are created from organic compounds that show the qualities of weak bases or acids. The responses of the transference of protons for these categories of substances are manifested by the structural modifications, disoperation or creation within the chromosphere sets. In the indicators that have a monochromatic quality, the chromosphere groups consist of only one of the classes of the indicators which may be deprotonated or protonated. In the indicators that are dichromatic, both the protonated and deprotonated chromosphere groups are present (Yakasai 62).

The indicators have an equilibrium that is primarily influenced by the ionic strength and the temperature of the solution. A modification in the ionic strength possessed by the solution has the potential of causing the equilibrium point to shift while changing the magnitude of the color of one or both types of the forms. As a result, while using the color of the acid base indicators in order to ascertain the pH, the saturation of the indicator must be equivalent in both solutions (Yakasai 62). The change in hue equilibrium for any specific ionic strength is expressed by the following equation:

pK_indicator  + log [H_ind] [H_Ind]^-1= pH

In the equation, the pK_a is applied as the constant that is applied to the indicator. The pH measuring range for the hibiscus has been estimated at between 3.0 and 7.5. This pK_a can be confirmed by the application of known acids and bases in the titration process which have confirmed pH values (Yakasai 62).

Works Cited

Ben Amor, B. & K. Allaf.” Impact of texturing using instant pressure drop treatment prior to solvent extraction of anthocyanins from Malaysian Roselle (Hibiscus sabdariffa).” Food Chemistry 115.3(2009): 820- 825.

Bhagai, Vishwas C., Radheshyam D. Patil, PR Channekar et al. “Herbal Indicators as substituent to synthetic indicators.” International Journal of Green Pharmacy 2.3(2008): 162- 163.

Ochani, Pooja C. & Priscilla D’Mello. ” Antioxidant and antiphyperlipemic activity of hibiscus sabdariffa Linn. Leaves and calyces extracts in rats.” Indian Journal of Experimental Biology 47.1(2009): 276- 2782.

UC Davis. “Henderson- Hasselbalch Approximation.” UC Davis, 2015. Web. 8 November 2015. <http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Buffers/Henderson-Hasselbalch_Approximation>

Yakasai, A. H. Musa, I. Hamisu et al. “On the use of Hibiscus sabdariffa flower extract flower extract as natural base indicator.” Chem Class Journal 2.1(2005): 62- 64.