Download AP Chem Stoichiometry Topic#4 Questions WS Name: Date: Per

AP Chem
Stoichiometry Topic#4
Questions WS
Name: _________________________________
Date: ______________________
Per#: ___
Questions:
(1) Naturally occurring magnesium has isotopic
abundances as shown.
(a) What is the average atomic mass of Mg?
(b) Sketch the mass spectrum of Mg.
(2) Glycine, an amino acid used by organisms to make proteins, is represented by the
molecular model.
(a) Write its molecular formula.
(b) Determine its molar mass.
(c) Calculate the mass of 3 moles of glycine.
(d) Calculate the percent nitrogen by mass in glycine.
(3) The diagram is a representation of 20 atoms of a fictitious element, which we will call
nevadium (Nv). The red spheres are 293Nv, and the blue spheres are 295Nv.
(a) Assuming that this sample is a statistically representative sample of the element,
calculate the percent abundance of each element.
(b) If the mass of 293Nv is 293.15 amu and that of 295Nv is 295.15 amu, what is the
atomic weight of Nv?
(4) Based on the structural formula, calculate the percentage of carbon by mass present in the compound.
(5) The diagram represents the collection of elements formed by a decomposition reaction. (a)
If the blue spheres represent N atoms and the red ones represent O atoms, what was the
empirical formula of the original compound? (b) Could you draw a diagram representing
the molecules of the compound that had been decomposed? Why or why not?
(6) The diagram represents the collection of CO2 and H2O molecules formed by
complete combustion of a hydrocarbon. What is the empirical formula of the
hydrocarbon?
In the diagram, the white spheres represent hydrogen atoms, and the blue
spheres represent nitrogen atoms. To be consistent with the law of
conservation of mass, how many NH3 molecules should be shown in the
right box?
(7) The diagram represents a chemical reaction in which the red spheres are
oxygen atoms and the blue spheres are nitrogen atoms. (a) Write the
chemical formulas for the reactants and products. (b) Write a balanced
equation for the reaction. (c) Is the diagram consistent with the law of
conservation of mass?
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(8) The following diagram represents a high-temperature reaction between
CH4 and H2O. Based on the reaction shown, how many moles of each
product can be obtained starting with 4.0 mol CH4?
(9) How many grams of water are produced in the
oxidation of 1.00 g of glucose, C6H12O6?
C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(l)
The steps in the solution can be summarized
as shown in the diagram.
(10)
The reaction between reactant A (blue spheres) and reactant B (red
spheres) is shown in the diagram. Based on this diagram, which
equation best describes the reaction?
(a) A2 + B → A2B
(b) A2 + 4 B → 2 AB2
(c) 2 A + B4 → 2 AB2
(d) A + B2 → AB2
(11)
Under appropriate experimental conditions, H2 and CO undergo
a combination reaction to form CH3OH. The drawing
represents a sample of H2. Make a corresponding drawing of
the CO needed to react completely with the H2. How did you
arrive at the number of CO molecules?
Because the H2 is completely consumed, it is the limiting reagent in
this case. Because there is a stoichiometric excess of O2, some is left
over at the end of the reaction. The amount of H2O formed is related
directly to the amount of H2 consumed.
(12)
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