In which two ways does a balanced chemical equation model the law of conservation of mass?
A. The total mass of the reactants equals the total mass of the
products.
B. The total mass of the metals involved equals the total mass of
nonmetals.
C. The reactants are the same substances as the products.
D. The same numbers and types of atoms appear on both sides of
the equation.

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

How many moles of gas are present if p=11 atm, v=12l, t=185k?

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)