GC Chemistry Questions

1. Explain the difference between the mass number of an isotope and the average atomic masson the periodic table. How would you calculate each?
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2. Name the molecule SeO2 and draw its Lewis structure. Then answer the following questions:
a. What process did you use for drawing the structure of SeO2?
b. How did you determine the correct number of bonds or lone pairs around the central
atom?
c. Describe the relative strength and length of the Se-O bonds.
d. What is the shape of the molecule?
e. Would you classify this molecule as polar or nonpolar? Justify your answer.
f.
What intermolecular forces would you expect to exist between SeO2 molecules?
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3. The unknown gas A2B forms according to the reaction below.
A(s) + B2(s) → A2B(g)
If 3.0 mol of A are reacted with 20.0 g of B2 (molar mass of B2 is 18.0 g/mol) in a sealed
container at STP, what volume would A2B occupy?
What would happen to the volume of the gas if the temperature of the container decreased while
pressure remained constant? Explain your answer in terms of the Kinetic Molecular Theory.
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4. Answer the following questions about a 0.35 M solution of HCN
a. Would you classify this solution as acidic or basic?
b. Is HCN considered strong or weak? How did you know?
c. How would you calculate the pH of the solution?
d. What would happen if 150.0 mL of 0.65 M NaOH was added to 150.0 mL of the
HCN solution? Draw a particulate level diagram showing what is in the solution of
just HCN and just NaOH before the reaction, and after they are mixed.
+
HCN Solution
→
NaOH Solution
Final Solution
i.
Calculate the pH of the final solution.
ii.
Would it be appropriate to use the equation M1V1 = M2V2 to perform
calculations for this reaction? Justify your answer.
e. What would happen if NaCN was added to the original HCN solution instead of
NaOH?
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