If 20.0mL of .2019M HCI requires 39.63mL of a NaOH solution for complete neutralization, what is the concentration of the NaOH solution? how many significant figures are justified in the answer?
HCl + NaOH ==> NaCl + H2O
mols HCl used = L x M = 0.0200 L x 0.2019 M = ??
mols NaOH (from the equation it is a 1:1 ratio of HCl to NaOH; therefore, mols NaOH must be the same as that for HCl).
mols NaOH = L x M
You have L (0.03963 mL) and you have mols (from HCl), calculate M NaOH. You can have as many s.f. as the least number in your calculations; therefore, you may have 3 since 20.0 mL has three.
To find the concentration of the NaOH solution, we can use the concept of stoichiometry. Stoichiometry involves calculating the amount of one substance in a chemical reaction based on the amount of another substance involved.
In this case, we know that 20.0 mL of 0.2019 M HCl reacts with 39.63 mL of NaOH. The balanced chemical equation for the neutralization reaction between HCl and NaOH is:
HCl + NaOH → NaCl + H2O
From the equation, we can see that they react in a 1:1 ratio. This means that one mole of HCl reacts with one mole of NaOH.
First, we need to calculate the number of moles of HCl present in 20.0 mL:
moles of HCl = volume (L) × concentration (M)
Converting 20.0 mL to liters:
20.0 mL × (1 L / 1000 mL) = 0.0200 L
Now, calculating the moles of HCl:
moles of HCl = 0.0200 L × 0.2019 M = 0.00404 mol
Since HCl and NaOH react in a 1:1 ratio, there are also 0.00404 mol of NaOH in the reaction.
Now, we can calculate the concentration of NaOH solution:
concentration (M) = moles of NaOH / volume (L)
Converting 39.63 mL to liters:
39.63 mL × (1 L / 1000 mL) = 0.03963 L
Calculating the concentration of NaOH:
concentration (M) = 0.00404 mol / 0.03963 L = 0.102 M
Therefore, the concentration of the NaOH solution is 0.102 M.
Now, let's determine the number of significant figures justified in the answer. Both the volume of HCl (20.0 mL) and the volume of NaOH (39.63 mL) are given to three significant figures. The concentration of HCl (0.2019 M) is also given to four significant figures.
To determine the number of significant figures in the answer, we look at the least precise measurement involved, which is the volume of NaOH (39.63 mL). Therefore, the concentration of the NaOH solution should be reported with three significant figures to match the least precise measurement.
So, the concentration of the NaOH solution is 0.102 M to three significant figures.