Module 4 Flashcards
An industrial chemist performs this reaction as part of a manufacturing process: 3Fe2O3 (s) + CO(g) -> 2Fe3O4 (s) + CO2 (g). She finds that when she starts with 3 moles of Fe2O3, she obtains 347 grams of Fe3O4. The molar mass of Fe3O4 is 231.55. What is her approximate percent yield?
75% (see pg. 161) - actual yield/theoretical yield x 100; in this case, the theoretical yield is 2 mols of Fe3O4, which weighs [2] x [231.55] = 463.10 grams; 347/463.10 x 100
The law of conservation of mass states that in a chemical reaction:
the total mass of the products must be equal to the total mass of the reactants
Which of the following choices is the correct solution for this problem: how many grams of C3H8 do you need to produce 132.0 grams of CO2? The balanced equation is: C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(g); the atomic mass of carbon in 12.01, of oxygen is 16.00, and of hydrogen is 1.01
44.0 grams
What is wrong with this chemical equation? (NH4)2SO4 + Pb(NO3)2 -> 2NH4NO3 + PbSO4
the physical states are not indicated
The relationship between the average mass of a single atom of an element (given in amu) and the mass of a mole of those atoms (given in grams) is:
the two quantities have the same numerical value
Which of the following chemical equations is not balanced? Physical states are left out for clarity.
Al(OH) + 3 HCl -> AlCl3 + H2O; When properly balanced, this should read Al(OH)3 + 3HCl → AlCl3 + 3H20
In a chemical reaction, the energy difference (measured as heat) between reactants and products is called the change in __________, while the change in order/randomness is called the __________ difference. A reaction which gives off heat is called __________ while one that requires heat is __________.
enthalpy; entropy; exothermic; endothermic
When a reversible chemical reaction reaches dynamic equilibrium, which of the following is true?
the rates of the forward reaction and the reverse reaction are equal
The law of conservation of mass states that in a chemical reaction:
the total mass of the products must be equal to the total mass of the reactants
How can you balance the following equation? HCl(aq) + Ca(s) -> CaCl2 (aq) + H2 (g)
put a coefficient of 2 in front of the HCl
1 atomic mass unit (amu) =
1.661 x 10-24 (coefficient) g
1 mol of atoms, or Avogadro’s number =
6.022 x 10 23(coefficient) atoms of an element
atomic mass
the average mass of a single atom in amu for any given element
molar mass
mass of 1 mol of atoms, in grams
what is the formula unit?
the smallest collection of atoms that provides the identity of the atoms present in a compound and the relative numbers of each type of atom
what is formula mass?
the addition of the masses of all the atoms or ions of which the unit is composed; to calculate, the formula unit must be known
the formula mass of 1 mol of a compound is its ____ ____ in units of g/mol
molar mass
If you put a teaspoon of ethanol-based herbal tincture into a cup of very hot tea, the ethanol will evaporate quite rapidly, leaving most of the extractives behind in the water. This tells you that:
the boiling point of water is higher than that of ethanol
Which of the following chemical equations is not balanced? Physical states are left out for clarity.
Al(OH) 3HCl -> AlCl3 H2O
