At the beginning, the solution had been filtered and the white precipitate was collected. The precipitate is known to be calcium oxalate. The filtrate was so obtained and used for the finding of the optical density by utilizing the atomic soaking up spectrometry ( AAS ) . The optical density of the Ca filtrate is increasing bit by bit as the concentration addition bit by bit. As more metal ion is present ( concentration addition bit by bit ) , they tend to clash with each other easy and do the optical density to increase when the concentration addition. Hence as concentration of the filtrate addition, the optical density besides addition. For general, the wavelength of Ca is 422.7 nanometer in the atomic soaking up spectrometry ( AAS ) .

Chloride is an anion ( oxidation province of -1 ) which means that it consist of a negatively charge. Whereas Ca is a cation ( oxidation province of +2 ) which means that it consisted of a positive charge. As Ca has the charge of +2 and chloride has the charge of -1 which is imbalanced, hence they are non stable.

In order to accomplish the stableness, 2 chloride ions are needed to adhere with 1 Ca ion. As this happen, it will do chloride ion to absorb strongly as this can be seen from the high soaking up value of chloride comparison to others ion. The depression of chloride is less than phosphate, this may due to the charge of these 2 ions.

Chloride is an anion and it will adhere with Ca to organize a stable and impersonal compound but as general, chloride have the oxidization province of -1 and therefore it will hold less energy that will by and large do it to hold less soaking up value. Whereas phosphate is a cation and it will adhere with Ca to organize a stable and impersonal compound but as general, phosphate have the oxidization province of -2 and therefore it will hold more energy that will by and large do it to hold more soaking up value.

The phosphate ions interfere with the finding of Ca. In the presence of phosphate ions, the soaking up due to the Ca is weaker as compared to that in which phosphate ions were eliminated. This may due to the formation of stable phosphate of Ca that does non easy interrupt up into atoms in the fire. The suppression by phosphate was relative up to a phosphate/calcium ratio of approximately 2:3, after which it became changeless. Hence, it is relative lessening in soaking up with increasing phosphate concentration.

High concentration of phosphate will hold changeless intervention. This is because phosphate inhibited the Ca soaking up strongly. As phosphate can respond with Ca ion and in the fire to bring forth Ca pyrophosphate, Ca2P2O7 that removes big Numberss of Ca atoms from the fire. This cause a decrease in the optical density since the Ca must be in the atomic signifier to absorb its resonance line. This type of solution interfere can be reduced or eliminated chemically. Hence, it will do the soaking up value to deject.

Optical density of Mg and aluminum

Magnesium

For Mg, there are big figure of ions was found that the Ca intervention were less serious in Mg at lower concentration but more serious at the higher concentration. The depression of aluminum was nonlinear and depended on the ratio of Ca to aluminum.

From the consequence above, there is suppression of Ca by Mg to a Mg/Ca ratio of 1and the soaking up is changeless. This shows that there is an sweetening of Mg atoms at the free Ca atoms. The wavelength of Mg is 285.2 nanometer in the atomic soaking up spectrometry ( AAS ) .

Aluminum

Calcium soaking up is capable to a figure of intervention when aluminum is added to it. This will do its signal to stamp down. The suppression by aluminum was chemical in nature. This component will respond as anions with Ca to give the Ca salt which is calcium aluminate. The wavelength of aluminum is 309.3 nanometer in the atomic soaking up spectrometry ( AAS ) . But in theoretical, Al can heighten the consequence of intervention. This status may be caused by ionisation of the aluminum itself as it contained high charge. The obtained consequence is wholly different from the theoretical consequence may be due to some proficient mistake and human mistake.

Comparison between Magnesium and Aluminium

The interfere with the finding of Ca from the aluminum is more than Mg. This may due to the different charge and form of aluminum and Mg. From the consequence obtained, aluminium depress more compared to magnesium because aluminum have 1 excess positive charge compared to aluminium. As it has more charge it will do the aluminum ion to be ionized more compared with the Mg that is lack of 1 positive.

On other manus, the size of the aluminum is by and large bigger than Mg. Bigger size of aluminum will do it to hold less energy compared to the Mg that has a smaller size. This cause aluminum to has less absorption value. As the wavelength of Mg and aluminum in the atomic soaking up spectrometry ( AAS ) are about the same, so it is sometimes hard to distinguish the soaking up set of the Mg and aluminum in the atomic soaking up spectrometry ( AAS ) .

Optical density of phosphate + 1 % EDTA

The optical density of phosphate and 1 % EDTA is somewhat lower than the optical density of phosphate without 1 % EDTA. This is because the suppression intervention have been overcome and minimized for phosphate in the nowadays of EDTA. When there is a high concentration of EDTA was added to the solution in order to organize a chelate is dissociated is the fire to give free Ca vapour.

EDTA was added for the finding of Ca in order to forestall intervention from phosphate because EDTA will protect Ca from adhering with phosphate. Hence, it will hold a lower soaking up value than the soaking up value of phosphate entirely.

Optical density of phosphate + 2000 ppm Sr

Strontium released Ca wholly from the foreign furnace lining metal, which is so complexed with chloride. When there is a presence of Sr in the phosphate, it cause the optical density of the solution to increase, this is because Sr can get the better of all the anionic interventions.

Strontium can move as a releasing agent that means that it can unite with the phosphate and forestall its reaction with the Ca. Hence, it will hold a higher soaking up value compared to the phosphate entirely and those that contain EDTA.

Remark:

Actually for the ions, the soaking up value that obtained should be all positive, but for the consequence obtained by experimentation for the 2nd, 3rd, 4th and 5th are all negative. This may due to some factor. The 1st factor is human mistake made during the experiment such as do non add the solution follow the concentration right, do non take some safeguard and the solution may be contaminated.

2nd factor that caused the negative value of the consequence obtained may be due to the proficient mistake such as the atomic soaking up spectrometry ( AAS ) that is used to find the optical density of the ions do non graduate good. Besides that, that machine used may non be maintain or fix for a long clip, o it will caused some inaccurate in the consequence that obtained.

Decision:

Part A:

Percentage ( % ) of precipitation of Ca oxalate is 99.97 % .

Part B:

The sum of Ca nowadays in H2O can be determined by fire atomic soaking up spectrometry.

The sequence for the depression in the optical density of the component is arranged in the falling order as followed:

( more ) Phosphate + 1 % EDTA & A ; gt ; Phosphate & A ; gt ; Magnesium and Aluminium & A ; gt ; Chloride & A ; gt ; Phosphate + 2000 ppm Strontium ( less )