What is the `[OH^(-)]` in the final solution prepared by mixing `20.0 mL` of `0.050 M HCl` with `30.0 mL` of `0.10 M Ba(OH)_(2)`?

What is the [OH^(-)] in the final solution prepared by mixing 20 mL of 0.050 M HCl with 30.0 mL of 0.10 M Ba(OH)_(2) ?

What is the [OH]^(-) in the final solution prepared by mixing 20.0mL of 0.050M HCl with 30.0 mL of 0.10 M Ba (OH)_(2) ?

What is the final [Na^(+)] in a solution prepared by mixing 70.0 mL of 3.00 M Na_(2)SO_(4) with 30.0 mL of 1.00 M NaCl?

What is the concentration of H^(+) in a solution that is prepared by mixing 50.0 mL of 0.50 M HCl with 200.0 mL of 0.25 M HCl ? Fill your Answer of the multiplying it with 10.