CZB190 prac report PDF

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This is the write up to the 1st practical done in CZB190...

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+EXPERIMENT 1 REPORT STUDENT NAME:

LAB SESSION AND DAY/DATE:

STUDENT EMAIL ADDRESS:

DEMONSTRATOR’S NAME:

A. Electrolytes – Data and Results

Sample # 1

Substance Tap water

Bulb brightness (bright, dim or none) none 30

Current (mA)

Electrolyte type (strong, weak or nonelectrolyte) Weak

Deionised water

None

0

none

Solid NaCl

None

0

none

190

Strong

70

weak

0

none

6

none

28

Weak

None

50

weak

bright

280

10

0.1M HCl(aq)

11

0.1M

Bright

220

2 3 4 5 6

7

8

9

bright 0.1M NaCl (aq) None 0.01M NaCl (aq) 1.1 M None C12H22O11(aq ) Ethanol None (C2H5OH ) 0.1 M None CH3COO H(aq) 1.1 M NH4OH( aq)

strong

strong

NaOH(aq)

12

13

0.1M Ba(OH)2(aq)

Bright

190

strong

1.0 M H2SO4(a q)

bright

300

strong

observations from procedure 6: Ba(OH)2(aq) + H2SO4(aq) → ?

Bulb brightness Current Bright bulb The current started  To dim at 220 “mA”  To nearly out  Then back to - 1 drop = 230 dim - 15 = 217 - 25 = 175  Then to - 40 = 220 bright

Other A precipitate occurred from the reaction. This is what caused the mA to drop as there were no easily available ions due to it being solid.

A. Questions A1. Suggest a reason why the electrical conductivity of tap water and deionized water might be different. - Because deionised water is pure and has no other elements present – therefore no extra ions are present. Tap water usually has metal ions or other elements present in the water which cause it to have increased conductivity. A2. Was there a difference in the conductivity of solid NaCl and of the 0.1 M NaCl solution and if yes, why? - Yes, there was a difference. In a NaCl solution, there are free electrons which are available to conduct electricity. However, in the solid NaCl there are no available ions as it is a solid and therefore cannot conduct electricity nearly as easily.

A3. Was there a difference in the conductivity of the two NaCl solutions and if yes, why?

Yes, there was a difference between the two NaCl solutions. Electricity can conduct through an electrolytic solution due to the presence of ions. The 0.1m concentration of NaCl would conduct electricity better because it has more ions present in the solution than the 0.01m solution of NaCl. A4. Was there a difference in the conductivity of 0.1 M NH 4OH solution and of the 0.1 M NaOH solution? If yes, suggest a reason for it. - Yes, there was a difference of conductivity between the solutions. NaOH is a very strong base and will fully dissociate in water. This disassociation will result in more ions present in the solution which will cause there to be a higher conductivity reading. NH4OH is a weak base and does not fully dissociate in water, therefore not producing as many ions and not as much conductivity. -

A5. The 0.1 M CH3COOH and 0.1 M HCl solutions had the same concentration of molecules when the solutions were made. Did they have the same concentration of ions in the solutions that were tested? What is the evidence? - They did not have the same number of ions in the solutions that were tested. HCl has more ions available and therefore has a bigger mA charge than CH3COOH. HCl had a mA of 280 while CH3COOH only had a mA of 28. A6. Explain your observations as Ba(OH) 2 solution was added gradually to the H2SO4 solution. Identify the products of the reaction and write a complete balanced equation. - Products formed: BaSO4 and 2H2O - Complete chemical equation = H2SO4 (aq) + Ba(OH)2 (aq) BaSO4 (s) + 2H2O (s) As the Ba(OH)2 was slowly added to the H2SO4, a precipitate began forming in the solution. This caused the solution to almost become fully solid.

B. Detection of Calcium Ions in Milk – Experimental data and calculations: 1

Mass of Ca2+ ions in 100 mL of milk (from the milk bottle) = 117 mg Mass of Ca2+ ions in 30 mL of milk (calculated) = 53.1 mg

Mass of watch glass + filter paper (m1) = 49.8807g Mass of watch glass + filter paper + precipitate (m2) = 50.1204g Mass of wet CaC2O4 precipitate (m2 – m1) = 50.1204 – 49.8807g = 239.7mg Mass of dry CaC2O4 precipitate (m2 – m1) = 49.8970 – 49.8807g = 16.3mg

Write the molecular equation for the detection of Ca2+ ions using ammonium oxalate ((NH4)2C2O4) solution: 1 Your demonstrator will provide this information

CaCl2 (aq) + (NH4)2C2O4 (aq)  CaC2O4 (s) + 2 NH4Cl (aq)

From the above equation, the mole ratio is: 2+¿ Ca¿ ¿ 1:1 n¿ ¿

Calculate the mass of calcium ions in the wet precipitate and based on that the experimental yield (%) of calcium ions: -

Moles of CaC2O4 = 0.2397g / 128.097g/mol = 1.87124 x 10-3

Compound % of calcium ions= (40.08/128.097) x 100 = 31% of compound Mass of compound = (1.87124 x 10-3) x 128.097 = 0.2397 g/mol 31% of 0.2397 = 0.074307g Therefore, the mass of calcium ions present in the dry precipitate is 74.307mg Calculate the mass of calcium ions in the dry precipitate and based on that the experimental yield (%) of calcium ions: -

Moles of CaC2O4 = 0.0163g / 128.097g/mol = 1.87124 x 10-3

Mass of compound = (1.272473204 x 10-4) x 128.097 = 0.0163 g/mol 31% of 0.0163 = 5.053mg Therefore, the mass of calcium ions present in the dry precipitate is 5.053mg

B. Questions B1. One food source of oxalic acid is rhubarb. How could you test it for the presence of oxalic acid? (You can support your answer with an equation) HCl could be used as it can dissolve oxolate crystals (so could be used at 1m). We can precipitate oxolate again at PH=4-5 with calcium nitrate, thus forming white crystals of calcium oxolate. Starting with a complex matrix, It would be easiest to use chromotography to separate and identify oxolate. B2. Oxalic acid and oxalate salts are found in many different foods. Why is it important to moderately consume foods that are particularly high in oxalates? As a matter of fact, for some patients, doctors recommend low oxalate (or oxalate-controlled) diet. What kind of patients should go on this type of diet? Patients who are at high risk of forming kidney stones would be suggested to use this diet as it will help reduce the possibilities of a kidney stone forming. A patient who is suffering from low mineral absorption in their diet would we then suggest using this diet as well....