# How many calcium ions is needed to displace hydronium ions in an strong acid ion exchange resin?

If 1 mole of Ca2+ can displace 2 moles of Na+ in an ion exchange resin, can it do the same for H+? Will Ca2+ ion displace 2 moles of H+ in a strong acid resin?

Yes, as $$\ce{1 Ca^2+}$$ displaces $$\ce{2 H+}$$.
No, as you need to involve more then $$\ce{1 Ca^2+}$$ to displace $$\ce{2 H+}$$ for exchange comparable with ionex capacity, as some $$\ce{Ca^2+}$$ passes through before $$\ce{H+}$$ is washed out.