Physical Chemistry Answers

Ingrid and Wahid are doing a chemical experiment.They take 2.4 grams of barium carbonate and add this to 25.0mL of water and notice that it does not dissolve completely.
i) What percentage of the barium carbonate will dissolve in the solution? Given Ksp of barium carbonate = 5.1*10^-9
ii)Subsequently, 5.0 mL of 1.0 mol L^-1 HNO3 is added to the mixture. Calculate the % of solid left.
iii) Another 10 mL of the HNO3 solution is added. They see bubbles appearing and all solid dissolves. Give the reaction that takes place and calculate the amount of gas formed and the pH of the final solution.
(ps: My problem with the question is in part iii. I calculated the mol of HNO3, but it doesn't seem to be enough to completely dissolve the barium carbonate. Is there an error in the question?)

A study of the reaction of bromide ion with bromate ion under acidic conditions, gave the following data:

reaction time(s) [Br-](mol L-1)
0.0 1.50 x 10-2
90.0 3.49 x 10-3

5 Br-(aq) + BrO3-(aq) + 6 H+(aq) --> 3 Br2(aq) + 3H2O(l)

If the initial concentration of H+(aq) for the experiment is 0.100 mol L-1 and the initial rate is 5.00 x 10-5 M s-1, calculate the concentration of H+(aq) after 20.0 seconds of reaction time, assuming that there is a negligible change in the rate of reaction.

What is the physical meaning Gibb's Free Energy?
Is it the amount of energy present in a system to perform chemical reaction(work) or the energy left after a reaction occurs which are given by the delta G values, i.e. when negative the reaction releases energy and when positive it absorbes energy?

How to determine the accurate conc of HCl acid if approximately 3 moldm^-3 HCl acid is provided?
I am suppose to plan an experiment in the lab to answer this question. I am provided with 1.00 moldm-3 NaOH and equipment and materials normally found in a school lab.

Why we chose 2H2O+2e--->H2+2OH- at cathode instead we chose O2+4H+ +4e--->2H2O at cathode?

What is meant by partial pressure of a gas in liquid?

what is the ph value of 10^ -13 acidic water?

A heat engine absorbs 760 kJ heat from a source at 380K. It rejects (1) 650 kJ, (ii) 560 kJ, (iii) 504 kJ of heat to sink at 280 K. State which of these represent a reversible, an irreversible and an impossible cycle.

Do Ideal Gases have mass or volume?
I got asked this question and I got really confused... When I tried to find a solution and many different answers came up. Some say that ideal gases have negligible mass and therefore virtually no volume. Some say that ideal gases have no volume but do have mass. Thank you for reading