$$Ca(NO_3)_2(aq) + Na_2SO_4(aq) → CaSO_4(s) + 2NaNO_3(aq)$$
In this reaction, calcium nitrate and sodium sulfate react to form calcium sulfate and sodium nitrate. The coefficients in front of each compound indicate the relative amounts of each substance that are involved in the reaction. For example, 1 mole of calcium nitrate reacts with 1 mole of sodium sulfate to produce 1 mole of calcium sulfate and 2 moles of sodium nitrate.
