(Cr2O7)2- + 2Al + 14H+ <—> 2Cr3+ + 2Al3++ 7H2O
1) how many ml of solution 1.50 M e (Cr2O7)2- are needed to act without residue with 0.8 grams of Al?
2) what is the concentration of the solution (Cr2O7)2-
I posted a qestion to you yesterday asking what 1.5 M e meant. No answer from you. I see you're still posting the error. This is a redox equation and the first thing you must do is balance the equation.
Hmm, chemistry is hard! Does anybody have the answer? :/ I'm better with math
To answer both questions, we need to use stoichiometry and the balanced chemical equation provided.
First, let's write down the balanced chemical equation:
(Cr2O7)2- + 2Al + 14H+ ↔ 2Cr3+ + 2Al3+ + 7H2O
Now let's solve each question step-by-step:
1) How many mL of a 1.50 M solution of (Cr2O7)2- are needed to react completely with 0.8 grams of Al?
Step 1: Determine the number of moles of Al
To find the number of moles of Al, divide the mass given by the molar mass:
Moal mass of Al = 26.98 g/mol
Number of moles of Al = 0.8 g / 26.98 g/mol
Step 2: Determine the stoichiometry between (Cr2O7)2- and Al
From the balanced equation, we see that the stoichiometry between (Cr2O7)2- and Al is 1:2. This means that for every 1 mole of (Cr2O7)2-, we need 2 moles of Al.
Step 3: Calculate the number of moles of (Cr2O7)2- needed
Since the stoichiometry between (Cr2O7)2- and Al is 1:2, the number of moles of (Cr2O7)2- needed is half the number of moles of Al:
Number of moles of (Cr2O7)2- = (0.8 g / 26.98 g/mol) / 2
Step 4: Calculate the volume of the solution (Cr2O7)2- needed
Use the molarity of the (Cr2O7)2- solution to calculate the volume needed.
Molarity = moles / volume (in liters)
Volume (in liters) = moles / molarity
Volume (in mL) = (moles / molarity) * 1000
Substitute the values:
Volume (in mL) = (0.8 g / 26.98 g/mol / 2) / (1.50 mol/L) * 1000
2) What is the concentration of the (Cr2O7)2- solution?
Since both questions are related, we can use the calculated volume from question 1 to find the concentration of the (Cr2O7)2- solution.
Concentration (in mol/L) = moles / volume (in liters)
Substituting the values:
Concentration (in mol/L) = (0.8 g / 26.98 g/mol / 2) / (Volume (in mL) / 1000)
how many moles of Al in 0.8g? Say, x.
You will need half that many moles of Cr2O7 -- x/2
x/2 moles * 1L/1.5moles * 1000mL/L = ____ mL