Sally carries out the following chemical reaction in an open container. MnO2 (s) + 4HCl (aq) MnCl2 (aq) + 2H2O (l) + Cl2 (g)

She finds that the total measured mass of the products is less than the mass of the reactants. How can she best explain this difference in mass between the products and reactants?

1Mass was not actually conserved in this reaction

2Because the products are all liquid or gas, they cannot be measured accurately

3The water formed in the reaction made up the mass of the chlorine gas that was released

4Some of the mass in the product was converted into gas, which was released into the air

Suppose a pair of chemical compounds a and b can react in two different ways: a + b -> c reaction 1 gives product c. a + b -> d reaction 2 gives product d. the following facts are known about the two reactions: . reaction 1 is endothermic and reaction 2 is exothermic. if a reaction vessel is charged (filled) with a and b , then at first d is produced faster than c. use these facts to sketch a qualitative reaction energy diagram for both reactions. note: because these sketches are only qualitative, the energies don? t have to be exact. they only have to have the right relationship to each other. for example, if one energy is less than another, that fact should be clear in your sketch.