When calcium nitrate and sodium hydroxide solutions are mixed, what precipitates out?

In their chemical formula, Calcium Nitrate is Ca (NO₃) ₂ while Sodium Hydroxide is NaOH. The reaction between the two are:

Ca (NO₃) ₂ + 2 NaOH → Ca (OH) ₂ + 2 NaNO₃

As you can see, this is a double replacement reaction. Focusing on the products, in an aqueous solution, NaNO₃ will dissolve in water because all nitrates are soluble. Ca (OH) ₂ is insoluble in water so this is the solid that precipitates.