1. A student wanted to measure the amounts of (Ca2+) in the human blood. She got 1.00ml which she treated with Na2C2O4 solution. The resulting Ca2C2O4 precipitate was filtered and dissolved in dilute H2SO4 to release C2O42- into solution and allow it to be oxidized. The solution required 2.05ml of 4.88 x 10-4 KMnO4 to reach the endpoint. The balanced equation is:
2KMnO4 + 5Ca2C2O4 + 8H2SO4 �¨ 2MnSO4 + 2K2SO4 + 5CaSO4 + 10CO2 + 8H2O
Write the:
(i) Net ionic equation for this reaction
(ii) Calculate the amount (in mol) of Calcium (Ca2+) used in this reaction.
(iii) Calculate the Calcium ion concentration expressed in units of milligrams (mg) Ca2+/100ml of blood.
i). With a balanced MOLECULAR equation, you should have no trouble writing a net ionic equation.
MnO4^- + C2O4^2- + H^+ ==>Mn^2+ + CO2 + H2O
Just plug in the coefficients.
ii). How many moles MnO4^- were used. moles = M x L = ??
Now use the coefficients in the balanced equation to convert moles MnO4^- to moles C2O4^- and that to moles Ca^+2
iii)grams Ca^2+ = moles Ca^2+ x atomic mass Ca^2+. Convert that to mg and that will be mg Ca^2+ per 1 mL. Multiply by 100 to find mg Ca^2+/100.
Post your work if you get stuck.
(i) The net ionic equation for the reaction can be derived by removing the spectator ions (ions that appear on both sides of the equation and do not participate in the reaction):
2Ca2+ + C2O42- + 2H2SO4 → 2CaSO4 + 10CO2 + 2H2O
(ii) To calculate the amount of calcium (Ca2+) used in the reaction, we can use stoichiometry and the volume of the KMnO4 solution used.
From the balanced equation, we can see that 2 moles of KMnO4 react with 5 moles of Ca2C2O4. Therefore, the number of moles of Ca2C2O4 can be calculated as follows:
Moles of Ca2C2O4 = (2.05 mL KMnO4) * (4.88 x 10^-4 mol KMnO4 / 1 mL KMnO4) * (5 mol Ca2C2O4 / 2 mol KMnO4)
= 0.0246 mol Ca2C2O4
(iii) To calculate the calcium ion concentration in milligrams per 100 ml of blood, we need to determine the molar mass of Ca2+ and convert the moles of Ca2C2O4 to milligrams.
The molar mass of Ca2+ is 40.08 g/mol.
Mass of Ca2C2O4 = (0.0246 mol Ca2C2O4) * (5 mol Ca2+ / 1 mol Ca2C2O4) * (40.08 g Ca2+ / 1 mol Ca2+)
= 19.83 g Ca2+
Now we can convert grams to milligrams:
Mass of Ca2+ (in mg) = 19.83 g Ca2+ * (1000 mg / 1 g)
= 19830 mg Ca2+
Finally, we can express the calcium ion concentration in units of milligrams (mg) Ca2+/100 ml of blood:
Concentration of Ca2+ = (19830 mg Ca2+) / (1.00 mL blood) * (100 mL / 1 dL) * (1 dL / 10000 mL)
= 198.3 mg Ca2+/100 mL blood
Therefore, the calcium ion concentration in the human blood sample is 198.3 mg Ca2+/100 mL blood.
(i) The net ionic equation for this reaction can be obtained by removing the spectator ions. In this case, the spectator ions are K+ and SO4^2-.
Net ionic equation: 5Ca2+ + 10C2O4^2- + 8H2SO4 → 5CaSO4 + 10CO2 + 8H2O
(ii) To calculate the amount (in mol) of Calcium (Ca2+) used in this reaction, we need to determine the number of moles of KMnO4 that reacted with Ca2C2O4.
From the balanced equation, we can see that the stoichiometric ratio between KMnO4 and Ca2C2O4 is 2:5. Therefore, the amount of Ca2C2O4 can be calculated using the following equation:
Amount (in mol) of Ca2C2O4 = (Amount of KMnO4 used * Stoichiometric ratio) / 5
The amount of KMnO4 used is given as 4.88 x 10^-4 mol, and the stoichiometric ratio is 2:5.
Amount (in mol) of Ca2C2O4 = (4.88 x 10^-4 mol * 5) / 2
(iii) To calculate the Calcium ion concentration expressed in units of milligrams (mg) Ca2+/100 ml of blood, we need to know the volume of blood used and the mass of Calcium (Ca2+) in that volume of blood.
The volume of blood used is given as 1.00 ml. Assuming the blood density is approximately equal to water (1 g/ml), we can assume that the mass of the blood is 1.00 g.
Now, we need to convert the amount of Calcium (Ca2+) in mol to the mass of Ca2+ in grams.
To do this, we need to know the molar mass of Ca2+. The molar mass of Ca2+ is approximately 40.08 g/mol.
Mass of Ca2+ = Amount of Ca2C2O4 * Molar mass of Ca2+
Finally, we can express the Calcium ion concentration in mg Ca2+/100ml of blood:
Calcium ion concentration = (Mass of Ca2+ / Volume of blood used) * (100 / Mass of blood) * 1000
Note: The factor of 1000 is used to convert the result from g/ml to mg/100ml.
I'll leave the calculations to you based on the given information.