Chemistry Assignment (Doc)
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Added on 2020-04-21
Chemistry Assignment (Doc)
Added on 2020-04-21
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Chemistry-Based Practical Report 1CHEMISTRY BASED PRACTICAL REPORTBy NAMECourseProfessor’s NameInstitutionLocation of InstitutionDate
Chemistry-Based Practical Report 2Chemistry-Based Practical ReportThe buffer capacity practical that was carried out in this unit is defined as the amount of moles of acid or base that is required to cause a variation of pH value of one liter of the solution by one unit. Buffer solutions are capable of maintaining a relatively constant pH value if only a little amount of acid or base is added and therefore this resistance to variations in pH can also be defined as buffer capacity[ CITATION Fre12 \l 1033 ].1.pH DefinitionpH is an abbreviation for the potential of hydrogen and it is a measure of how much acidic or alkaline an aqueous solution is[ CITATION Jor11 \l 1033 ]. It is represented by the equation belowpH=-log[H+]The “p” in pH implies that it is power of 10 since the scale is a logarithmic function and thus implying that for values that are below 7 on the pH chart, acidity increases by a factor of 10 down the pH chart and for values above 7 on pH chart each value denotes acidity decreases by a factor of 10 up the pH chart. 2.Dissociation of weak acidsWeak acids do not dissociate fully in solutions thus they do not give all the hydrogen ions to the solution. Calculation of pH of weak acids needs one to take into account unique ionization constant (Ka) and equilibrium concentration[ CITATION Bri13 \l 1033 ]. They are very important in preparing buffer solutions. Ka is normally very smallin weak acids while pKa is always high. Generally, dissociation is represented as shown in the equation below;
Chemistry-Based Practical Report 3HA(aq)⇌H+(aq)+A-(aq)Where HA is the species to be dissociated while A- is the acid conjugate. The above equation shows that dissociation is reversible.Ka can be expressed as shown in the equation belowKa =[A ̅]¿¿Ka from the above equation shows the ease with which an acid releases its proton and it can also be noted how dissociation of weak acids change with respect to the H+ level in the solution.pKa which is used as an index to represent the acidity of weak acids can be defined by the equation belowpKa =-logKa3.Preparing pH Buffered SolutionA pH buffered solution is made by adding a base or an acid to a known volume of salt solution. Normally a strong acid or a strong base is added to a salt whose concentration is known[ CITATION Ste10 \l 1033 ]. The salt is assumed to be neutral thus able to maintain a constant pH value and the addition of base or acid may not cause a change in the pH unless the salt solution is completely reacted on after which the pH value may rise or fall drastically.4.Acid-Base Titration Generic PrinciplesAcid-Base titration aids in the determining the unknown concentration of an acid when it is neutralized by a known concentration of base and vice-versa. The neutralization leads to the production of a salt and water[ CITATION Joh13 \l 1033 ]. Normally a color indicator is applied
Chemistry-Based Practical Report 4to the titer normally in a flask before starting the titration process for ease of identifying when the point of neutralization is nearing. In titration, neutralization is achieved at a pH of 7 and at that point the solution is said to be at equilibrium and always accompanied by the production of water and a salt. An example can be as shown in the equation below H2SO4(aq)+2NaOH(aq)→Na2SO4(s)+2H2O(l)5.Buffer CapacityThis refers to the number of moles of an acid or a base that can initiate a variation in pH value of one liter of the solution by a unit. It gives an indication of a solutions ability to resist a variation in pH by consuming hydrogen or hydroxyl ions[ CITATION CsT13 \l 1033 ]. It is denoted by β and mathematically represented asβ=∆B∆pHWhere ∆B =quantity of strong acid or strong base per gram that can change the pH value of 1L of buffer solution and∆pH =variation in pH due to the addition of a base or an acid.6.Maximum Buffering CapacityAs one adds a strong acid or a strong base to a buffered solution, there is a drastic change of pH up to a point when the concentration of basic components equals the concentration of acidic components. Buffer solution exhibit optimum buffering capacity when pH=pKa, a point at which the buffer solution is capable of resisting drastic variations in the value of pH in response to the addition of acid or base[ CITATION Phi13 \l 1033 ]. According to Henderson-Hasselbach equation
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