i need help for the three questions

An aqueous solution contains 0.26M ammonia. One liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) (Select all that apply.) 0.26molCaI2 0.27molHBr 0.13molHBr 0.27molNH4I 0.13molBa(OH)2 An aqueous solution contains 0.30M ammonium nitrate. One liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) (Select all that apply.) 0.29molNH3 0.14molHCl 0.14molNaOH 0.29molKNO3 0.30molHCl An aqueous solution contains 0.32M hydrofluoric acid. One Liter of this solution could be converted into a buffer by the addition of: (Assume that the volume remains constant as each substance is added.) (Select all that apply.) 0.08molCa(OH)20.33molKF0.16molHI0.32molKBr0.33molHI