(2) Boiling is a common method of softening hard water in life, in which a large number of calcium and magnesium ions are converted into precipitation. The principle of alum water purification is that after alum is dissolved in water, it generates colloid to absorb the impurities suspended in water and precipitate them. Chlorine mainly plays a role in disinfection and sterilization in the preparation of tap water.
3 From the perspective of balanced nutrition, vitamins cannot be lacking in food, so Xiao Ming should also supplement vegetables, fruits or foods rich in vitamins; According to the data, the total intake of protein by Xiao Ming is calculated. Total protein = 250g×10%+25g×14%+200g× 20%+250g× 3% = 76g, so it does not meet the standard.
(2)① Taking it after chewing can increase the reaction contact area and speed up the reaction;
② The reaction between sodium bicarbonate and hydrochloric acid will generate carbon dioxide, which will aggravate the condition of gastric ulcer. The equation is nahco3+HCl = NaCl+H2O+C02 ↑;
So the answer is (1)① carbon and nitrogen;
② Boil water; Alum is dissolved in water to form colloid, which absorbs impurities suspended in water and precipitates; Sterilization and disinfection;
3 vegetables and fruits or rich in vitamins; Not reached;
(2)① increasing the contact area of reactants to speed up the reaction; ②nah co 3+HCl = NaCl+H2O+CO2↑；