Can you check if this is correct please?
a) How many moles of sodium hydroxide are there in 19.00 cm3 of 0.100 mol dm3?
My answer: 0.0019 mol
b) How many moles of hydrochloric acid are, there in 25.00 cm3 of the acid solution?
My answer: 0.0019 mol
c) How many moles of hydrochloric acid are, therefore in 1000cm3 of solution?
My answer (this is the one I'm unsure about): 0.0076 mol
I did 0.0019 x 1000/25.00
d) What is the concentration of the hydrochloric acid solution?
My answer: 0.076 mol dm3
I am stuck on this though:
The concentration of hydrogen ions in a 0.1 mol dm3 solution of phosphoric acid, H3PO4?
I would be able to do it if I knew the correct equation that = H3PO4 but I can't work it out.
If any of these are wrong can you please explain how they should be done thank you :)
You don't have enough information to help you.
a is right.
b--What acid solution? If this is a titration the answer is ok.
c--If this is NaOH titrated with HCl both c and d are correct.
For the last (un-lettered) question you have, H3PO4 is a triprotic acid. k1 = about 10^-3, k2 = about 10^-8 and k3 = about 10^-13.
So you set up an ICE chart and calculate the concn H^+.
............H3PO4 ==>H^+ + H2PO4^-
initial.....0.1.......0......0
change......-x........x.......x
equil......0.1-x......x........x
Essentially you ignore k2 and k3 since they are so much smaller than k1.
k1 = (H^+)(H2PO4^-)/(H3PO4)
Look up k1, subtitute the ICE data into the k1 expression and solve for H^+ = x.
Thank you. I know, the question was very long so I tried to shorten it for this but left out some details sorry!
To check if your answers are correct, I will go through each question one by one:
a) How many moles of sodium hydroxide are there in 19.00 cm3 of 0.100 mol dm3?
To solve this, you need to use the formula:
Number of moles = Concentration (mol dm3) x Volume (dm3)
In this case, the concentration is given as 0.100 mol dm3, and the volume is given as 19.00 cm3. However, it's important to convert the volume to dm3 before calculating. Since 1 cm3 is equal to 1 x 10^-3 dm3, the volume is:
19.00 cm3 x (1 x 10^-3 dm3/1 cm3) = 0.019 dm3
Now, you can calculate the number of moles:
Number of moles = 0.100 mol dm3 x 0.019 dm3 = 0.0019 mol
Your answer of 0.0019 mol is correct.
b) How many moles of hydrochloric acid are there in 25.00 cm3 of the acid solution?
Using the same formula as above, with the given concentration of the solution (not provided) and the volume of 25.00 cm3, it's not possible to determine the number of moles without the concentration.
c) How many moles of hydrochloric acid are there in 1000 cm3 of the solution?
To find the number of moles in this case, you can use the information from the previous question and the concept of proportionality. If the number of moles in 25.00 cm3 is 0.0019 mol, you can set up the equation:
Number of moles in 25.00 cm3 / Volume of 25.00 cm3 = Number of moles in 1000 cm3 / Volume of 1000 cm3
Plugging in the values, you have:
0.0019 mol / 25.00 cm3 = x mol / 1000 cm3
Solving for x, you get:
x = (0.0019 mol / 25.00 cm3) x 1000 cm3 = 0.076 mol
Your answer of 0.076 mol is correct.
d) What is the concentration of the hydrochloric acid solution?
To find the concentration, you need to know the number of moles of hydrochloric acid and the volume of the solution. Without the number of moles provided, it is not possible to solve this question.
Regarding the last question about the concentration of hydrogen ions in a 0.1 mol dm3 solution of phosphoric acid, H3PO4, it is important to note that phosphoric acid can exist in different forms with different ionization levels. Without specific information on whether the acid is fully ionized or partially ionized, it is not possible to determine the concentration of hydrogen ions.
In summary, your answers to questions a, c, and d are correct. Question b requires additional information, and the last question cannot be determined without more specific information about the ionization level of phosphoric acid.