chem part 4
What is the enthalpy for a two-step reaction, given for the two steps are +206 kJ and -136 kJ, respectively?
+70kj
Suppose that a chemical equation can be written as the sum of two other chemical equations. If two reactions have values of -658 kJ and +458 kJ, what is for the reaction that is their sum?
-200Kj
A 5.0 g sample of silver is heated from 0°C to 35°C and absorbs 42 J of energy as heat. What is the specific heat of silver?
0.24J/(g)(c)
For the reaction represented by the equation SO3 + H2O ® H2SO4, how many grams of sulfuric acid can be produced from 200. g of sulfur trioxide and 100. g of water?
245g
How much energy is absorbed as heat by 20. g of gold when it is heated from 25°C to 35°C? The specific heat of gold is 0.13 J/g·°C.
26J
If a piece of aluminum is heated from 40.0C to 70.0C, what is the value of ?
30.0K
For the reaction represented by the equation 2KlO3 ® 2KCl + 3O2, how many moles of potassium chlorate are required to produce 250. g of oxygen?
5.21 mol
For the reaction represented by the equation 2Fe + O2 ® 2FeO, how many grams of iron(II) oxide are produced from 8.00 mol of iron in an excess of oxygen?
575 g
For the reaction represented by the equation CH4 + 2O2 ® CO2 + 2H2O, how many moles of carbon dioxide are produced from the combustion of 100. g of methane?
6.23 mol
For the reaction represented by the equation 2Na + Cl2 ® 2NaCl, how many grams of sodium chloride can be produced from 500. g each of sodium and chlorine?
824 g
For the reaction represented by the equation Mg + 2HCl ® H2 + MgCl2, calculate the percentage yield of magnesium chloride if 100. g of magnesium react with excess hydrochloric acid to yield 330. g of magnesium chloride.
84.2 percent
DH =
Hproducts - Hreactants
What is the measured amount of a product obtained from a chemical reaction?
actual yield
The Greek letter D stands for
change in
Spontaneous reactions are driven by
decreasing enthalpy and increasing entropy
Which of the following is a measure of the randomness in a system?
entropy
The majority of spontaneous chemical reactions in nature are
exothermic
is always negative for a
exothermic reaction
As ice melts, the water molecules
go from a well-ordered phase to a less-ordered phase
Which of the following is transferred due to a temperature difference?
heat
What units are used to measure energy as heat?
joules or kilojoules
In an endothermic reaction, the total energy at the beginning of the reaction is
less than the total energy at the end of the reaction
For an endothermin reaction, is always
positive
When the limiting reactant in a chemical reaction is completely used, the
reaction stops
What is the energy required to raise the temperature of 1 g of a substance by 1°C or 1 K?
specific heat
Which of the following is a measure of the average kinetic energy of the particles in a sample of matter?
temperature
A piece of metal is heated, then submerged in cool water. Which statement below describes what happens?
the temperature of the water will increase and the temperature of the metal will decrease
What is the maximum possible amount of product obtained in a chemical reaction?
theoretical yield
In a calorimeter, the energy content of a substance is calculated from measurement of the temperature change in a known mass of
water
