3. Students measured the mass of the reactants and products for a combustion reaction they observed.
When they measured the mass of the products, they discovered the products had a greater mass than
the reactants. How did this unexpected change in mass occur?
A. Stadents made a measurement error, because ending with more products is impossible.
B. The reactants had hidden materials within them that had no mass until the reaction was complete.
C. The products of reactions often have greater mass, because the law of conservation is not
applicable in all chemical reactions.
D. The reaction occurred in an open system, so during the reaction a gas interacted with the reactants.
The mass of the gas could not be measured before the reaction.
Answers: 3
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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.)
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What is the subscript for oxygen in its molecular formula
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The atomic number, or number, is the described as the number of in the nucleus of an chemical element.
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