# Equivant mass of double salt

What is the equivalent mass of double salt like dolomite? And what if the double salt is hydrated?

Is a double salt taken as a single unit while equating the gram equivalent in any reaction? For example, in reaction

$$\ce{CaCO3.MgCO3 + 4 HCl -> CaCl2 + MgCl2 + 2 CO2}$$

is

$$\frac{\text{wt of dolomite}}{\text{eq wt of dolomite}} = \frac{\text{wt of}~\ce{CO2}}{\text{eq wt of}~\ce{CO2}}?$$

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$$\ce{CaCO3.MgCO3}$$ reacts with $$\ce{4 HCl}$$, therefore $$m_\mathrm{eq}=m/4$$.
$$\ce{CaCO3}$$ reacts with $$\ce{2 HCl}$$, therefore $$m_\mathrm{eq}=m/2$$.
$$\ce{MgCO3}$$ reacts with $$\ce{2 HCl}$$, therefore $$m_\mathrm{eq}=m/2$$.
$$\ce{Na2CO3.10 H2O}$$ reacts with $$\ce{2 HCl}$$, therefore $$m_\mathrm{eq}=m/4$$.
$$\ce{1 CO2}$$ of carbonate origin is released by $$\ce{2 HCl}$$, therefore $$m_\mathrm{eq}=m/2$$.