To solve the question you use the following formula:
concentration (1) × volume (1) = concentration (1) × volume (1)
3 M × volume (1) = 1.8 M × 50 mL
volume (1) = (1.8 M × 50 mL) / 3 M = 30 mL
To determine the expected pH of the resulting solution of the following substances, create a balanced chemical equation of their ionization in water:
HI
HI + H2O ---> H+ + I-
It completely dissociates into H+ and I-. Due to the presence of the Hydronium Ion, the solution is acidic.
KBr
KBr + H2O ----> HBr + KOH
The salt KBr is formed by a strong base and a weak acid, therefore, the solution it forms with water is basic.
LiOH
LiOH + H2O ----> Li+ + OH-
It dissociates completely in water, turns into Li+ and OH-. Due to the presence of Hydroxide Ion, the solution becomes basic.
You have already gotten the balanced equation. And the ratio of mol number of reactants and production is the ratio of coefficient. So there is 6.4/8*11=8.8 mol oxygen needed. The mass is 8.8*32=281.6 g.