What is the law of conservation of mass and how is it related to the results of a chemical reaction?

Brad and his family like to go camping. they always take a gas lantern with them. the lantern can take fiuels but always puts out the same amount of light. brad has two different kinds of fuel for the lantern. how can he figure out which kind of fuel has more chemical energy that the lantern can turn into light? measure the brightness of the lantern using each kind of fuel by comparing it to the full moon. g measure the volume of the containers of fuel. measure how long the lantern stays lit on a fixed amount of fuel. measure the mass of each container of fuel using a balance scale. answer 12

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

In france, grapes are 1.95 euros per kilogram. what is the cost of grapes, in dollars per pound, if the exchange rate is 1.14 dollars/euro? (2.6)