Indicate the concentration of each ion or molecule present:
a mixture of 48.0 mL of 0.11 M KClO3 and 28.0 mL of 0.29 M Na2SO4. Assume the volumes are additive.
a) [K+]
b) [ClO3-]
c) [SO42-]
d) [Na+]
We haven't taken notes on this particular type of problem yet and I can't find tutorials on the internet. Do I have to find the number of moles of each substance, then add them or something similar? I'd appreciate if someone could show me how to do at least one so I can figure out the rest on my own.
The problem asks for concentration and probably that means M or mols/L (or millimols/mL). So you want to find the mols of each ion, divide by total volume and that will be M. I prefer to find millimols and divide by mL.
For 48 mL 0.11 M KClO3 you have 48 x 0.11 = 5.28 millimols. The total volume is 48.0 mL + 28.0 mL =76.0 mL. So (KClO3) is 5.28mmols/76.0 mL = 0.06947 M which I would round to 0.0695 to three significant figures. Now that you know the (KClO3) you know (K^+) = 0.0695 M and (ClO3^-) = 0.0695 M. You do Na2SO4 the same way. Remember, though, after you have (Na2SO4), the (Na^+) will be 2x (Na2SO4) because there are 2 Na^+ per molecule Na2SO4.
There is another way to do this that I think is easier. You're mixing two substances and each dilutes each other; i.e., the 0.11M KClO3 is diluted from 48.0 mL to 76.0 mL so the new concentration is 0.11 M x (48.0/76.0) = 0.0695M with (K^+) = (ClO3^-) = 0.0695 M.
For Na2SO4, it is
0.29 M x (28.0/76.0) = 0.1068 which I would round to 0.107 M. That gives you (Na^+) = 2*0.107 = ? and (SO4^2-) = 0.107 M.
To find the concentration of each ion or molecule in the mixture, you need to follow a few steps:
1. Calculate the number of moles of each substance using the formula:
moles = concentration (M) x volume (L)
2. Convert the moles into the concentration by dividing the moles by the total volume of the mixture.
3. Finally, consider the stoichiometry of the compound to determine the concentration of each ion or molecule.
Let's start with part (a) and calculate the concentration of [K+].
a) [K+]:
First, calculate the moles of KClO3:
moles of KClO3 = 0.11 M x 48.0 mL = 5.28 mmol (millimoles)
Next, convert the volume of KClO3 to liters:
48.0 mL = 48.0 mL x (1 L / 1000 mL) = 0.048 L
Now, calculate the concentration of K+ ions by considering the stoichiometry. Since KClO3 has a 1:1 ratio of K+ to KClO3, the concentration of K+ ions will be the same as the concentration of KClO3.
So, [K+] = 0.11 M (the concentration of KClO3)
You can follow a similar process to find the concentration of [ClO3-], [SO42-], and [Na+]. Remember to calculate the moles of each species from their concentrations and volumes, convert volumes to liters if necessary, and consider the stoichiometry of the compounds.