"Determine the volume of a 0.925M K2Cr2O7 solution required to completely react with 5.28g of Cu."
My attempted method for solving was to convert the 5.28g of Cu to moles, find moles of K2Cr2O7 using the mole to mole ratio, and then use M=mol/L to solve for volume. Here is the chemical equation I came up with...
K2Cr2O7 + 2Cu -> Cu2Cr2O7^- + 2K^+
I'm not really sure what I'm doing wrong, but I think it may have something to do with the equation I came up with above.
Your approach is correct, but the chemical equation you provided is incorrect. The correct balanced equation for the reaction between K2Cr2O7 and Cu is:
2K2Cr2O7 + 3Cu → 3CuCr2O7 + 4K+ + 7O2
To determine the volume of the K2Cr2O7 solution required to completely react with 5.28g of Cu, you need to follow these steps:
Step 1: Convert the mass of Cu to moles.
Use the molar mass of Cu (63.55 g/mol) to convert 5.28g Cu to moles:
5.28g Cu × (1 mol Cu / 63.55g Cu) = 0.0831 mol Cu
Step 2: Determine the mole ratio between Cu and K2Cr2O7.
From the balanced equation, you can see that the mole ratio between Cu and K2Cr2O7 is 3:2. This means that for every 3 moles of Cu, you need 2 moles of K2Cr2O7.
Step 3: Calculate the moles of K2Cr2O7.
Use the mole ratio to find the moles of K2Cr2O7 required:
0.0831 mol Cu × (2 mol K2Cr2O7 / 3 mol Cu) = 0.0554 mol K2Cr2O7
Step 4: Apply the concentration formula to determine the volume.
The formula for concentration is Molarity (M) = moles / volume (L). Rearrange the formula to solve for volume:
Volume (L) = moles / Molarity
Given that the concentration of the K2Cr2O7 solution is 0.925M, we can substitute the values:
Volume (L) = 0.0554 mol K2Cr2O7 / 0.925 M = 0.06 L or 60 mL
Therefore, the volume of the 0.925M K2Cr2O7 solution required to completely react with 5.28g of Cu is 60 mL.
Your approach to solving the problem is correct, and you are on the right track. However, the chemical equation you provided is not balanced correctly. Let's first balance the equation and then proceed with the calculations.
The correctly balanced equation for the reaction between K2Cr2O7 and Cu is:
2K2Cr2O7 + 3Cu -> 3CuCr2O7 + 4K+
Now, let's proceed with the calculations step by step:
Step 1: Convert the mass of Cu to moles.
To do this, we need to use the molar mass of Cu.
Molar mass of Cu = 63.55 g/mol
Number of moles of Cu = mass of Cu (g) / molar mass of Cu (g/mol)
= 5.28 g / 63.55 g/mol
= 0.083 moles of Cu
Step 2: Determine the mole ratio between Cu and K2Cr2O7.
From the balanced equation, we see that for every 3 moles of Cu, we require 2 moles of K2Cr2O7.
Mole ratio = 2 moles K2Cr2O7 / 3 moles Cu
Step 3: Calculate the moles of K2Cr2O7 required.
To find the moles of K2Cr2O7, we multiply the moles of Cu by the mole ratio.
Moles of K2Cr2O7 = moles of Cu * (2 moles K2Cr2O7 / 3 moles Cu)
= 0.083 moles Cu * (2/3)
= 0.055 moles K2Cr2O7
Step 4: Use the molarity equation to find the volume of the solution.
The Molarity (M) of the solution is given as 0.925M. Molarity is defined as moles of solute per liter of solution.
Moles of solute = 0.055 moles K2Cr2O7
Molarity of solution = 0.925 M
We can rearrange the Molarity equation to solve for volume:
Volume (L) = Moles of solute / Molarity of solution
Volume = 0.055 moles K2Cr2O7 / 0.925 M
= 0.0595 L
= 59.5 mL
Therefore, the volume of the 0.925M K2Cr2O7 solution required to completely react with 5.28g of Cu is approximately 59.5 mL.