Is it a physical or a chemical change?

Why are the trends and exceptions to the trends in ionization energy observed?

The following reaction shows sodium carbonate reacting with calcium hydroxide. na2co3 + ca(oh)2 → naoh + caco3 how many grams of naoh are produced from 20.0 grams of na2co3? (molar mass of na = 22.989 g/mol, c = 12.01 g/mol, o = 15.999 g/mol, ca = 40.078 g/mol, h = 1.008 g/mol) 12.2 grams 15.1 grams 24.4 grams 30.2 grams

What is the molarity of 60.0 grams of naoh dissolved in 750 milliliters of water? a) 1.1 m b) 2.0 m c) 12 m d) 75 m