help finding pH values and with calorimeter problems

Hello, If you can please tell me how to find these answers.

find the pH of a solution containing 6 g HCl in 0.25 L of solution

find the ph of 0.15 M Ba(OH)2

find the pH of 0.5 L of HCl solution with a pH of 1.72 to a final volume of 1L

find the pH of 35. mL of 0.5 M HClO4 and 45mL of 0.600 M KOH

2. find amount of acid or base needed to prepare each solution

how many mL of M HNO3 is needed to prepare 1.0 L of 0.25 M HNO3

How many grams of HF to prepare 500 mL of 0.1M HF solution

How many grams of NaOH to prepare 200 mL of 2.5 M NaOH

3. Determine the pH of a solution when 100 mL of 0.50 M NH3 is mixed with 200 mL of 0.300 M NH4Cl

4. What is the pH if 0.01 mol of HCl were added to the solution in part 3?

5. A styrofoam cup calorimeter contains 150 grams of H20. the addition of 1430 J of heat produced a temp rise of 1.93 degree C. this date was used to calculate the calorimeter heat capacity: C cal=114 J /C. The dissolution of a small amount of salt in 150 grams of water caused the initial temp of 25 degree C to rise to 29.36 degree C. Calculate the q for the dissolution of salt. you may assume that the mass of the solution is 150 grams and that the heat capacity of the solution of water + salt is 4.184 J/g Celsius

Thank you for any help you can provide

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In answer to the first

In answer to the first question, you need to find the concentration first.
use the formula n = m/Mr to find the amount of moles:
6/36.4609 = 0.1645598436 moles
then use the formula c = n/V to calculate concentration:
0.1645598436/0.25 = 0.6582393742 mols/L
to find the potential of hydrogen (PH), you need to use this formula:
PH = -log(concentration H+)
so PH = -log(0.6582393742) = 0.1816161429

so PH is 0.18 approximately

I need some help: NaCN,

I need some help:
NaCN, sodium cyanate is dissolved in H2O. the molarity of the solution of the solution is 0.0010. Kat is 4.9x10^-10. Find the Ph?

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