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A sample contains an unknown amount of oxalic acid, H2C2O4. If 0.5187 g of the sample requires 40.20 mL of 0.

Q1. A sample contains an unknown amount of oxalic acid, H2C2O4. If 0.5187 g of the sample requires
40.20 mL of 0.1000 M NaOH to neutralize the H2C2O4 completely, what is the percentage of H2C2O4 in the
sample? The molar mass of H2C2O4 is 90.035 g/mol. The balanced equation for the reaction is:
H2C2O4 + 2 NaOH ® 2 H2O + Na2C2O4

Q2. You have 0.3991 g of an unknown monoprotic acid, HA, which reacts with NaOH according to the
balanced equation
HA + NaOH ® NaA + H2O
If 35.30 mL of 0.1086 M NaOH is required to titrate the acid to the equivalence point, what is the molar
mass of the acid?

Q3. (a) What element belongs to the 3rd period and Group 8A?
(b) What element belongs to the 5th period and Group 4B?

Q4. (a) Write the full electronic configurations of the following elements:
(i) Ne (ii) Si (iii) V (iv) I
(b) Using the symbol of the previous noble gas to indicate the core electrons, write the electronic
configurations of the same elements as in part (a).

Q5. (a) Using the symbol of the previous noble gas to indicate the core electrons, write the electronic
configurations of atoms in the following elements:
(i) Cs (ii) Cl (iii) As
(b) How many valence electrons are there in each of the above atoms?
(c) When the above elements form an ion, what charge is each of them likely to have?
(d) Using the noble gas notation, write the electronic configurations of the ions formed in part (c).

Q6. Use your knowledge of periodic trends for the following questions! Do not look up the answers;
trends are the important thing.
(a) Place the following elements in order of increasing size: Ga, Cs, Ca, Sr.
(b) Place the following elements in order of increasing first ionization energy: Ca, Si, Al, Rb.

Q7. Write the chemical equations for the first ionization energy of each of the following elements.
Specify the states of reactant(s) and product(s). HINT: A chemical equation contains one or more reactants
and one or more products.
(a) I (b) Al

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