9. When a candle has been burning for an hour, its mass is less than it was at the beginning. (a) How is it possible for the candle to lose mass without violating the law of conservation of mass? (b) How might you find the mass of the missing material? 14. Hydrochloric acid reacts with zinc. The chemical equation
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
9. When a candle has been burning for an hour,
its mass is less than it was at the beginning.
(a) How is it possible for the candle to
lose mass without violating the law of
conservation of mass?
(b) How might you find the mass of the
missing material?
14. Hydrochloric acid reacts with zinc.
The chemical equation for this reaction is
Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq)
a) Classify this reaction.
(b) Name the product that forms bubbles
in this reaction. How do you know?
c) How does the mass of zinc metal
change as the reaction proceeds?
d) What does the (aq) symbol in the
equation mean?
24. Consider this chemical equation:
Zn + 2 AgNO3 → Zn(NO3)2 + 2 Ag
a) How many atoms of zinc are on the left
side of the equation? How many are on
the right?
(b) How many atoms of silver are on the left
side of the equation? How many are on
the right?
(c) Is the equation balanced? Explain.
25.How are coefficients different from
subscripts in equations?
30. Consider this neutralization reaction:
HCl + NaOH → NaCl + H2O
a) Which substances are the reactants?
(b) Which product is an ionic compound?
(c) Name the reactants and products.
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