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In this experiment, we investigated the solubility of alkali hydroxides, specifically Ca(OH)2, LiOH, NaOH, and KOH, by titrating them against HCl. The solubility of these hydroxides was determined by measuring the concentration of the saturated solutions. The results were analyzed to understand the trends in solubility related to the periodic table and ionic bonding characteristics.
When alkali metals from groups one and two of the periodic table combine with OH molecules, they form ionic bonds. In this type of bonding, metals lose electrons, becoming positively charged ions, while non-metal ions/molecules gain electrons, becoming negatively charged.
The attraction between oppositely charged ions leads to the formation of a rigid 3-D lattice structure.
Due to their polar nature, ionic compounds are usually soluble in polar solvents like water. This solubility occurs because water is a polar molecule with a partial positive (δ+) and partial negative (δ-) charge on its atoms.
The solubility of a solute in water at a given temperature is the maximum amount that will dissolve in 100 grams of water at that temperature, resulting in a saturated solution.
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In this experiment, we aim to determine the concentrations of saturated solutions of Ca(OH)2, LiOH, NaOH, and KOH by titrating them against HCl, a strong acid.
Our hypothesis is based on the periodic trends: as you move down groups one and two, the atomic radii of the atoms increase, making the hydroxides more soluble. Conversely, as you move across a period, the solubility decreases due to smaller atomic radii and increased ion charges, resulting in stronger electrostatic attractions within the lattice structure.
Apparatus:
1. Determining Concentration of Ca(OH)2 solution:
Add four drops of phenolphthalein.
2. Calculating Concentration of LiOH, NaOH, and KOH
| Stage of Dilution | LiOH | NaOH | KOH |
|---|---|---|---|
| 1 | Pipette 10cm3 into a 250cm3 volumetric flask. | Pipette 25cm3 into a 250cm3 volumetric flask. | Pipette 25cm3 into a 250cm3 volumetric flask. |
| 2 | Make up to 250cm3 with distilled water. | Make up to 250cm3 with distilled water. | Make up to 250cm3 with distilled water. |
| 3 | Shake 40 times to ensure solution is uniform. | Shake 40 times to ensure solution is uniform. | Shake 40 times to ensure solution is uniform. |
| 4 | Pipette 25cm3 of diluted solution into a new volumetric flask. | Pipette 25cm3 of diluted solution into a new volumetric flask. | Pipette 25cm3 of diluted solution into a new volumetric flask. |
| 5 | Make up to 250cm3 with distilled water. | Make up to 250cm3 with distilled water. | Make up to 250cm3 with distilled water. |
| 6 | Shake 40 times to ensure solution is uniform. | Shake 40 times to ensure solution is uniform. | Shake 40 times to ensure solution is uniform. |
3. Calculate the concentrations of each diluted solution:
LiOH
NaOH
KOH
4. Select a suitable concentration of HCl to titrate with for each solution (based on 1:1 ratio):
| Diluted Solution | Diluted Concentration (moldm-3) | HCl Concentration (moldm-3) |
|---|---|---|
| LiOH | 0.2064 | 0.2 |
| NaOH | 1.05 | 0.1 |
| KOH | 1.71 | 0.2 |
5. Titrate the selected concentrations of HCl against the diluted solutions and record the titre value at the point of neutralization. Repeat the experiments as before.
6. Calculate the experimental concentrations of each saturated solution.
In order to determine the most concentrated alkali hydroxide, we will use stoichiometry and calculations to calculate the experimental values of the concentration of the saturated solutions.
The results of the titration experiments are summarized in the following table:
| Alkali Hydroxide | Experimental Concentration (moldm-3) |
|---|---|
| Ca(OH)2 | 0.0152 moldm-3 |
| LiOH | 0.0514 moldm-3 |
| NaOH | 0.102 moldm-3 |
| KOH | 0.165 moldm-3 |
The results obtained from the titration experiments will be discussed in this section. We will analyze the experimental concentrations of the saturated solutions and draw conclusions regarding the solubility of the alkali hydroxides.
In this experiment, we determined the concentrations of saturated solutions of Ca(OH)2, LiOH, NaOH, and KOH by titrating them against HCl. Based on the experimental values, we will draw conclusions about the relative solubility of these alkali hydroxides.
Based on our findings, we may make recommendations for further experiments or applications related to the solubility of alkali hydroxides. These recommendations will depend on the specific outcomes of our study.
There are several potential sources of error in this experiment that must be considered. These errors include inaccuracies in measuring, dilution, titration, and variations in room temperature. To improve the accuracy and reliability of the results, it is important to address and minimize these errors as much as possible.
Proper safety precautions were taken during this experiment to handle corrosive substances like KOH, NaOH, LiOH, and HCl. Eye protection and gloves were worn, and pipette fillers were used to prevent contact with these hazardous chemicals. Safety guidelines from Cleapss Hazcards were followed to ensure a safe laboratory environment.
Lab Report: Solubility of Alkali Hydroxides. (2020, Jun 01). Retrieved from https://studymoose.com/document/comparing-concentration-alkalis-saturated-solutions-new
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