Question

Q3) A drug compound for anticancer treatment, Platinol has a base structure of Pt(NH₃)₂Cl₂. A variant form of the drug has the formula Pt₂(NH₃)₄Cl₃. For the variant form, calculate the mass percent of platinum.

hint: Molar masses used Pt 195.084g/mol, N 14.0067g/mol, H 1.008g/mol, and Cl 35.453 g/mol.

Q4) When Barium (density is 3.5 g/mL) reacts with sulfur (density is 2.04 g/mL) to form barium sulfide, each barium atom reacts with one sulfur atom. The mass ratio of barium to sulfur in BaS is 137.3/32.06 or 4.283. You require 4.283 times as much mass Barium compared to sulfur to form BaS. Calculate the ratio of barium to sulfur when 2.316 cm³ of barium reacts with 1.49 cm³ of sulfur. Record your answer with 3 decimal places.

Q5) Fluoride ion is poisonous in relatively low amounts: 0.21 g of F^- per 61.3 kg of body weight can cause death. Nevertheless, in order to prevent tooth decay, fluoride ions are added to drinking water at a concentration of 1.3 mg of fluoride ion per L of water. How many kilograms of sodium fluoride would be needed to treat a 193698 gallon reservoir of water?  

Q6) A calibrated flask was filled to the 25.00mL mark with ethyl alcohol. By weighing the flask before and after the addition of ethanol, it was determined that the flask contained 18.526g. In a second experiment, 26.813 g of metal beads were added to the same flask, and filled with alcohol to the mark. The total mass of alcohol and metal beads in the flask was determined to be 40.978 g. What is the density of the metal in g/mL? Record your answer to two decimals.

Q7) Brass is a yellow alloy formed from copper and zinc. A brass cylinder has a length of 2.51 in and a diameter of 0.56 in. What is the mass of brass in this cylinder?

Helpful information:

You may assume that brass is 72 % copper (density is 8.83 g/mL) and the rest is zinc (density is 7.15 g/mL)

Use the concept of weighted density here to get an idea of density of brass and assume that the density of brass varies linearly with composition.

Answer 1

we address a simple conceptual question, namely, when two molecules A and B interact to form the complex AB, how large is the entropy change as a result of this interaction? The free energy has the generic form

G=H-TS,

where H is the enthalpy and S is the entropy.

We see that in a simple case in which there is no enthalpy change, the entire free energy balance is dictated by entropy. If a reaction increases the entropy this means there is a corresponding negative free energy change, signaling the direction in which reactions will spontaneously proceed. A deep though elusive insight into these abstract terms comes from one of the most important equations in all of science, namely,