A student measures 10.5 g of mercury(II)oxide into an open test tube and heats the tube.The heat causes the mercury(II)oxide to decompose into mercury and oxygen.After reaction,the student finds the mass of the contents of the tube to be 9.7 g.Which one of the following describes these observations?
A)The decomposition of mercury(II)oxide does not obey the Law of Conservation of Mass.
B)0)8 grams of oxygen gas are lost from the tube.
C)There are errors associated with the student's measurements.
D)Heating destroys some mass.

Question

Quizplus · Accepted Answer

According to the Law of Conservation of Mass, the total mass of the reactants and products in a chemical reaction should be the same. However, in this case, the mass of the products (mercury and oxygen) is less than the mass of the reactant (mercury(II)oxide). This can only be explained if some of the oxygen gas has escaped from the open test tube during the reaction. Therefore, option B is the best choice.

A Student Measures 10