paraphrase the lab

Abstract

The maximum amount of solute dissolving in a solvent produces a saturated solution. For example, aquatic species are kept alive by dissolution of oxygen to help them breathe. Under some conditions, the saturated solutions are made to be supersaturated. In order to determine the best method of determining solubility, different conditions were used and Ksp determined by the use of the solubility of one mole of the hydroxide ion.

Ksp was found to be 4.12, 1.17, and 2.64respectively. In comparison to the known values of ksp of calcium hydroxide which is 4.68, there is a percent error of 11.9%, 2400%, and 464.1% respectively.

The results showed that the first method gave results that were close to the theoretical value.

Introduction

Solubility has many uses like the dissolution of sugar in tea but also has demerits like the dissolution of poisonous chemicals in water.

The experiment determines the best solubility for Calcium hydroxide and uses comparison method to calculate the Ksp mathematically. Method one was more accurate because solubility increases with increase in the temperature.

To determine Ksp, we first experimentally determine the molarity of the dissolved products. Calcium hydroxide is obtain by the reaction between Calcium and water then separating by filtration.

Ca(s) + H2O → Ca(OH)2(s) (1)

Testing for the solubility of the solute in the solvent can be done by applying temperature in the solution. Solubility increases with the increase in the temperature because of the increased kinetic energy. Increased kinetic energy breaks the solute.

KE = 0.5 • mv2 (1)

m= mass

v= speed

Alternatively, titration can be used where HCl is titrated against Calcium hydroxide. According to Le Charteliers principle, there will be a shift in the reaction. The pH can be found by

Ca(OH)2(s) Ca2+(aq) + 2OH−(aq) (2)

[OH] = 10 (2)

In method 2 nad 3, equation numbers are used but in 3 the molr mass equationi sused to determine the moles of calcium hydroxide. The two can thus be used to find Ksp

Ksp = [X] [ Y] (3)

Molar mass = (4)

Moles = (5)

Molarity= (6)

The result obtained is compared to the theoretical to determine the best method determined

Data

Table1: Data table showing the collected resulted from method one.

Table2: Data table highlighting the collected results from method two.

Table3: The collected results from method three.

Result

From the GravimetricDetermination, calcium hydroxide is filtered and collected. It is placed in a beaker and heated using an oven to increase the rate of solubility.

Moles = = 2.02

Molarity = = 0.01M Ca(OH)2

Ksp = 4x

Ksp = 4( 0.01)4.12

In method 2, logger pro is used in determining the pH of filtered solution. Equation 2 is used as shown below

[OH] = 10= 0.0617 [OH]

Ksp = (0.0614)= 1.17

With titration, the experiment concludes when the pH is almost 7. By using the volume of HCl moles of the hydroxides could be determined. Using equation 3 Ksp is found as

7.5 ml = 3.75mol OH

Molarity = = 0.0375 [OH]

Ksp = (0.0375) = 2.64

The percentage error from the theoretical values are then calculated as

Method 1 %error= = 11.9%

Method 2 %error = = 2400%

Method 3 $error = = 464.1%

Table 4: Data table summarizing the result of the experiment.

From the table a ksp value of 4.12 was found in method 1 which is the closest to the literature value which is 4.68. This indicate that temperature gave a big impact in the solubility of the solution.

Discussion

Ksp determination is difficult but this method uses comparison to get the best procedure to be used. In this lab, the three methods used obtained different Ksp values because they were subjected to different conditions. The first method used temperature, the second the pH and the third; the lowet percent error i.e the nearest Ksp value to the theoretical one was assumed to be more correct. Though each method had their own results, here were potential challenges like error in weighing the beaker which could have raised the Ksp value. Another error could have occcured during the titration when the burette was rinsed with water instead of HCl. The water reacted with the acid and this reduced its strength hence solubility decreased..

A closed system and precise equipment could yield better results.

Questions:

1. The Ksp value is below the truevalue because HCl reacted with water to reduce the solubility.

2. The Ksp would remain constant since ng phenophthalein had no effect on the value of Ksp since it’s just an indicator