Physical Chemistry Answers

A recently graduated chemistry student got employed as a secondary school teacher. His task was to design some interesting experiments that involved computing, maths and chemistry to be displayed at the open day to attract more students to choose science.

His experiments involved mixing some chemicals and observing the colour change. He noticed that if one of the reactant's volume was varied, the time taken for colour of the solution to change also varied. So he obtained the results and tabulated them.  Using these data, explain what important information can be calculated. 

Time for the colour to change: 1m20s, 1m10s, 50s, 45s, 35s, 30s, 25s, 22s

Volume of reactant: 1, 2, 3, 4, 5, 6, 7, 8

A jet engine releases 5000j of energy per cycle and performs 800j work.

1. How much heat is absorbed by this engine per cycle.

2. What is the thermal efficiency

3. How much work this engine perform in a cycle

4. If this engine complete each cycle in 20sec, what is the power rating of this engine.

Show that work done W=q2 - q1

A solution contains 20.0g of NaCl in 750ml distilled water is found to have an absorbance of 2:52 at 520nm when the path length is 1cm. Calculate the molar absorptivity with units.

MgCO3(aq) + 2HCl(aq)  MgCl2(aq) + CO2(g) + H2O(l)

... and so the active constituent is the carbonate dianion, CO32-, with Mg2+ being an inert counter ion…

CO32-(aq) + 2H+ (aq)  CO2(g) + H2O(l)

Some tablets also contain aluminium hydroxide, which acts in a similar way...

Al(OH)3(aq) + 3HCl(aq)  AlCl3(aq) + 3H2O(l)

... and so the active constituent is the hydroxide anion, with Al3+ being an inert counter ion…

HO-(aq) + H+ (aq)  H2O(l)

The Asda Extra Strength brand contains 0.0882 g of CO32- and 0.121 g of HO- in each tablet.

(i) What mass of Mg2+ is present in each tablet? Show your reasoning/calculation.

(ii) What mass of Al3+ is present in each tablet? Show your reasoning/calculation.

(iii) What total volume of 0.25 M HCl (in cm3) is required to react with the MgCO3 and the Al(OH)3 present in one tablet? Show your reasoning/calculation.

A buffer solution of 0.20M acetic acid and Sodium acetate. Calculate the range in pH upon adding 1.0ml of 0.10m hcl of this solution

How many moles of electrons are required to produce

Methanol is produced according to the following equation:

CO(g) + 2H2(g) ⇄ CH3OH(g)

In an experiment, 1.000 mol each of CO and H2 were allowed

to react in a sealed 10.0-L reaction vessel at 500 K. When the

equilibrium was established, the mixture was found to contain

0.0892 mole of CH3OH. What are the equilibrium

concentrations of CO, H2 and CH3OH? Calculate the

equilibrium constants Kc and Kp for this reaction at 500 K?

(R = 0.0821 L.atm/Mol.K)

you push a statioinary wall with a force of 1000N. how much work was done to the wall?

Consider the scenario where 50 mg of copper and 10 mL of 0.2 M nitric acid were mixed. The reaction that occurs is:

Cu(s) + HNO3(aq) = Cu(NO3)2(aq) + NO2(g) + H2O(l)

All of the gas formed from this reaction is collected over water in the same manner as the lab; the volume obtained was 20.52 mL. What percentage of the starting copper was consumed in this reaction? Assume room temperature (22 degrees Celcius) and atmospheric pressure (1 atm) for your calculations.