Reactions and trends of group 1 and 2 metals are common questions asked at GCSE- Ca + 2 H2O ==> Ca(OH)2 + H2This reaction will be exothermic and happen slowly in cold water compared to G1 metals, magnesium will only react with water in the presence of steam.
moles = Mass/ Mr Mr(Ca) = 40.08Mass = 3 g moles = 0.07485 ... 0.0749 3sf