In any chemical reaction, the mass of the reactants equals the mass of the products. This result forms the basis of the Law of Conservation of Mass. Which statement correctly explains why this is a law, rather than a theory? It has more scientific evidence supporting it.

It has both independent and dependent variables.

It has been tested with the latest laboratory balances, which are very accurate.

It describes a repeatedly observed relationship, but it does not offer an explanation.

For a research project, a student decided to test the effect of the lead(ii) ion (pb2+) on the ability of salmon eggs to hatch. this ion was obtainable from the water‐soluble salt, lead(ii) nitrate, which the student decided to make by the following reaction. pbo(s) + 2 hno3(aq) → pb(no3)2(aq) + h2o losses of product for various reasons were expected, and a yield of 86.0% was expected. in order to have 5.00 g of product at this yield, how many grams of pbo should be reacted? (assume that sufficient nitric acid, hno3, would be used.)