Consider the following acid/base reaction CO3^2− + 2H^+ → H2O + CO2 that produces CO2 gas. 6 L of CO2 is collected at STP. What is the molarity of the HCl solution used in the reaction if 81 mL of HCl was needed?
6 L CO2. Knowing that 1 mol of any gas occupies 22.4 L at STP, then
6/22.4 = ? mols CO2.
Then using the coefficients in the balanced equation, that many mols CO2 x 2 = mols HCl used
Then M HCl = mols HCl/L HCl = ?
To calculate the molarity of the HCl solution used in the reaction, we need to use the given information about the reaction and the volume of CO2 gas collected.
First, let's start by calculating the number of moles of CO2 gas collected at STP. We know that 1 mole of any gas at STP occupies 22.4 L. Given that 6 L of CO2 gas is collected, we can calculate the number of moles as follows:
Number of moles of CO2 = Volume of CO2 (in L) / Volume of 1 mole (22.4 L)
= 6 L / 22.4 L
≈ 0.268 moles
According to the balanced equation, 1 mole of CO2 is produced for every 2 moles of HCl used. Therefore, the moles of HCl used in the reaction is half the moles of CO2 produced, which is:
Moles of HCl = 0.268 moles / 2
= 0.134 moles
Next, we need to convert the volume of HCl used into liters. We were given that 81 mL of HCl was used. Converting this to liters gives us:
Volume of HCl (in L) = 81 mL / 1000 mL/L
= 0.081 L
Finally, we can calculate the molarity (M) of the HCl solution using the formula:
Molarity (M) = Moles of solute / Volume of solution (in L)
Molarity = 0.134 moles / 0.081 L
≈ 1.654 M
Therefore, the molarity of the HCl solution used in the reaction is approximately 1.654 M.