Select the choice that best answers each question or completes each statement.
(1)The Hfus of ethanol (C2H5OH) is 4.60 kJ/mol. How many kilojoules are required to
melt 24.5 g of ethanol at its freezing point?
A. 2.45 kJ
B. 5.33 kJ
C. 245 kJ
D. 18.8 kJ
Chalk Review Activity
Chalk is a pure substance.
1. A 5.00-g sample of chalk has 2.00-g of
Calcium, 0.60-g of Carbon, and 2.40-g of
oxygen. Determine the empirical formula of
2. Using a balance and a piece of chalk
determine the number of molecules
Calculating Average Atomic Mass:
Natural carbon is composed of 98.93% carbon-12
(exactly 12 u) and 1.07% carbon-13 (13.00335 u).
2) How many liters of oxygen will be needed to
burn 100 liters of carbon monoxide? (answ: 50 L)
(0.9893)(12 u) + (0.0107)(13.0
Chemical Reactions and Stoichiometry
SAT Chemistry with Wolfe Four
Molecules = Two or more atoms joined by
Diatomic Molecules = A molecule of just
two atoms (regardless of whether they're the
same element or not)
7 Elements exi
Bond Enthalpies and the Enthalpies of Reactions:
Average bond enthalpies (click for a chart) can be used to estimate whether a reaction will
be endothermic (H > 0) or exothermic (H < 0).
Hrxn = (enthalpies of broken bonds) (enthalpies of bonds formed)
The study of energy and its
transformations is known
is commonly defined as the capacity
to do work or to transfer heat.
is energy used to cause an object with
mass to move.
is energy used to cause the temperature