HELP how do you do these two?? how do you do the work and what are the answers step by step?? URGENT

Use the following information to answer written response question # $2 .$

Strontium carbonate is the compound that gives off the red color in fireworks.

The enthalpy of formation of strontium carbonate from its elements can be calculated given the following three reactions:

  

  

 

 

Written Response #2

a) Determine the molar enthalpy of formation of strontium carbonate from its. (4 marks)

 

b) Sketch a potential energy diagram to illustrate the energy involved in the formation reaction. (5marks) (Al.4s, Al.5k) including Ea

                    ______________ Title

The dissociation of H2PO4- to HPO4-2 has a pKa of 7.2. For a 0.2 Mphosphate buffer at
pH 7.5, calculate the following values.

a. the ratio of HPO4-2 to H2PO4-
b. the concentrations of HPO4-2 and H2PO4-

The answer:
a. Ratio of HPO4^-2 to H2PO4- = 2.0
b. [HPO4 ^-2] = 0.133M; [H2PO4-] = .067M

How do you get these answers (step by step please!)

Calculate the pH of solutions prepared by:

a) dissolving .20 g of Na2O in water to give 100.0 mL ofsolution

b) dissolving 1.26 g of pure nitric acid in water to give .500 L ofsolution

c) diluting 40.0 ml of .075 M Ba(OH)2 to a volume of 300.0mL

Please show answers in step by step, for some reason I keepgetting the wrong answers :(

BaBr_2(aq)+Na₂SO_4(aq)--->?

im reading the chapter right now and dont understand thesemuch. How do you do these and when do products becomesolid?