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Why is elemental zinc considered a pure substance

A) it is a metal

B) it is a mixture of different atoms

C) it must be created in a lab

D) all elements are considered pure substances

What is the atomic mass of an atom that has 6 protons, 6 neutrons, and 6 electrons? a) 6 b) 8 c) + 1 d) 12 e) 18

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.