Question 2: Use your balanced equation to calculate the volume of 0.12 M Na3PO4 to stoichiometrically react with the 3.0 mL of Co (NO3)2. Show your work.
3) Discuss how your supernatant color in the 6 different test tubes supports your calculated result in #2. For example, if you used less than the volume of sodium phosphate calculated in #2, what would be the limiting reactant and does the observed supernatant color support this.
Why is the supernatant important when determining the limiting regents. ALSO would I use molarity to solving question 2?
See your previous post. I'm overwhelmed!
Those are the instructions but I just need help with this question. I balanced the reaction between cobalt ii nitrate with sodium phosphate. And I wanted to know why they supernatant liquid color was important when I mixed these two solutions together. I observed a purple color solid when the reaction occurred and the supernatant was red/pink.
From what I can gather from that long string of instructions the idea is to determine the solubility of Co3(PO4)2. I believe the idea is that Co(NO3)2 is colored. So when it reacts with the Na3PO4 it ppts the Co ion as the phosphate (solid) and settles (or is centrifuged) to the bottom. If ALL of the Co ion has reacted the supernatant liquid will be colorless; if there is still some Co ion not yet ppted it will be colored. The more Co ion that is un-precipitated the more intensely colored the supernatant liquid will be.
In many cases one can use molarity to determine limiting reagent but in some cases no; therefore I always go with mols to determine the limiting reagent. If you have M and volume, then mol = M x L. When working with small quantities like this I often use millimols. mmols = mL x M and when it comes time to convert back to M the easy way is M = mmols/mL.
Where Co(NO3)_2 is the limiting reagent the mmoles of the precipitate will be related to the mmoles of Co(NO3)_2 originally present by the balanced stoich. and the filtrate will be colorless?
And if Na_3PO_4 is the limiting reagent the filtrate will be red/pink?
This is my balanced eq.
3Co(NO3)_2(aq) + 2Na_3PO_4(aq) ==> CO_3(PO_4)_2(s)+6NaNO_3(aq)
_ =subscript
The supernatant is important when determining the limiting reactant because it helps to confirm whether the reaction has reached completion or not. The supernatant refers to the liquid portion in a mixture that settles above a solid precipitate or sediment.
In the given question, the volume of 0.12 M Na3PO4 is being calculated to stoichiometrically react with 3.0 mL of Co(NO3)2.
To solve this problem, you would first write the balanced equation for the reaction between Na3PO4 and Co(NO3)2:
2 Na3PO4 + 3 Co(NO3)2 -> Co3(PO4)2 + 6 NaNO3
Based on the balanced equation, you can see that the molar ratio between Na3PO4 and Co(NO3)2 is 2:3. This means that for every 2 moles of Na3PO4, you need 3 moles of Co(NO3)2 to react completely.
To calculate the volume of 0.12 M Na3PO4 needed to react with the given 3.0 mL of Co(NO3)2, you can use the following steps:
1. Convert the volume of Co(NO3)2 to moles using its molarity. You have 3.0 mL of Co(NO3)2, so you would use the following conversion:
Moles Co(NO3)2 = (3.0 mL) * (0.12 mol/L) = 0.36 mmol
2. Use the molar ratio from the balanced equation to determine the moles of Na3PO4 needed. In this case, the ratio is 3 moles of Co(NO3)2 to 2 moles of Na3PO4. You can set up a proportion:
(0.36 mmol Co(NO3)2) * (2 mol Na3PO4 / 3 mol Co(NO3)2) = 0.24 mmol Na3PO4
3. Convert the moles of Na3PO4 to volume using its molarity. The molarity of Na3PO4 is given as 0.12 M, and we want to find the volume in liters:
Volume Na3PO4 = (0.24 mmol) / (0.12 mol/L) = 2.0 mL
Therefore, the calculated volume of 0.12 M Na3PO4 needed to react stoichiometrically with 3.0 mL of Co(NO3)2 is 2.0 mL.
Regarding the second part of your question, yes, you would use molarity to solve question 2. The molarity (M) is a measure of the concentration of a solute in a solution and is expressed as moles of solute per liter of solution. In this case, the molarity of Na3PO4 is given as 0.12 M, and it is used to calculate the volume of Na3PO4 needed to react with Co(NO3)2.