Step-by-step explanation:
The reaction between Phosphoric Acid + Rubidium Hydroxide will form Water + Trirubidium Phosphate.
So, we have 3 H+ and to form H2O, we need 3 OH-, because of this, we need to balance the equation. So, let's put a 3 in front of RbOH:
H3PO4 + 3 RbOH → H2O + Rb3PO4
Also, now we have 3 H+ and 3 OH-. So it will form 3 H2O:
H3PO4 + 3 RbOH → 3 H2O + Rb3PO4
Balanced equation:
H3PO4 + 3 RbOH → 3 H2O + Rb3PO4
Answer: H3PO4 + 3 RbOH → 3 H2O + Rb3PO4