Table of Contents

Graph

worship the datasheet data data data

the organics

Organic Chem Questions Organic Cheat sheet Empirical formula questions

The Acid base cheatsheet

Pranav Question

a) in the first stage of the production of nitric acid, ammonia is reacted with oxygen to produce nitrogen monoxide.

A hot platinum catalyst is used. The reaction is highly exothermic, and the heat given out by the reaction is sufficient to maintain the temperature needed to give a fast rate.

The system is at equilibrium until t1 and then at t1, the volume of the vessel is reduced at constant temperature. Equilibrium is re-established at t2.

$4NH_{3} + 5O_{2} \rightleftharpoons 4NO + 6H_{2}O$ , $\Delta H<0$

Sketch the rate-time graph for the forward and reverse reactions to show the changes in rate until the return to equilibrium

b) Using "increase, decrease or no change" in the table below, identify the effect of reducing the volume of the mass and concentration of NH_3 and NO once equilibrium has been re-established.

NH3 NO
Mass
Concentration

c) The second stage involves the reaction of nitrogen monoxide with more oxygen to form nitrogen dioxide. $2NO + O_{2} \to 2NO_{2}$

At t0, 2.5 mol of NO and 1 mol of $O_{2}$ was injected into a 500mL container. At t1, equilibrium was re-established with only 1 mole of NO remaining.

Use this information to construct a detailed graph for how the concentrations of $NO_{2}$, $O_{2}$ and $NO_{2}$ varied between t0 and t1

a question about funny buffers

"An unknown mass of $HCl$ was accidentally spilled into a swimming pool of volume $5.00\times10^6 L$ by a maintenance staff member. To determine the mass of $HCl$ dropped, the technician took a $22.10 mL$ solution of $HCl$ and titrated this solution with standardised $0.1210 molL$ $NaOH$ solution. The titration was carried out using a pH monitoring machine. The titration was stopped when $35.40mL$ of $NaOH$ has been added. At this point the pH of the resulting solution was measured to be exactly 9.7 as excess $NaOH$ had been added and thus the solution was now a consistent pink(as phenolphthalein indicator was used)."

a) Determine the concentration of $HCl$ in ppm that was present in the swimming pool after the mishap if the density of the poll solution is $1.318gmL^{-1}$.

$$\begin{align} [H^{+}] = 10^{-pH} = 10^{-9.7}=1.995\times 10^{-10} molL^{-1} \\ \text{Assume }25° C\text{, }\therefore K_{w}=[H^{+}][OH^{-}], \therefore [OH^{-} ] =\frac{1\times \times 10^{-14}}{1.995\times 10^{-10}}=5.01\times 10^{-5}molL^{-1} \\ n=cV, \therefore n(OH^{-}) = 5.01\times 10^{-5} \times 0.02210= 1.11\times 10^{-6}mol \\ n=CV, \therefore n(OH^{-} \text{ added}) = 0.1210\times 0.03540=4.28\times 10^{-3} mol\\ \therefore n(OH^{-} \text{reacted}) = n(OH^{-} \text{ added}) - n(OH^{-}) = 4.28\times 10^{-3} - 1.11\times 10^{-6} = 4.28 \times 10^{-3} mol \\ OH^{-} + HCl \to Cl^{-} + H_{2}O \\ \therefore \text{1:1 ratio, } n(HCl) = n(OH^{-}) = 4.28 \times 10^{-3}mol \\ \end{align} $$

b) THe person carrying out the titration noticed that the pH metre recorded a sharp increase near the equivalence point but as the volume of $NaOH$ added increased and the solution colour remained pink, the pH maintained at a very high value and increased gradually. Explain these two observations with reference to the appropriate chemical principals. You may refer to the pH curve given.

(The pH curve given starts acidic and goes basic, equivalence is at neutral (7))

How Nick Lucarelli structures imf questions

Big hint

Malic acid is a lot less able to dissolve in water, due to a reduced hydrogen bonding capability.

The real stuff

Revise systematic, random error, probably make a list of systematic, random error for titrations.

A $200mL$ sample of wine was diluted to $250mL$ of water. $25mL$ of the diluted wine was titrated against $0.085molL^{-1}$ NaOH with an average aliquot of $20.55mL$

Assuming tartaric acid is the only acid $\implies$ find its concentration in $gL^{-1}$ and comment on whether its dry or sweet

Recall that 7-8.5 is sweet, 6-7.5 is dry

Recall that tartaric acid is essentially the same as malic acid, but tartaric acid has extra -OH

literally biology

catalysts

when to double layer for chemistry

reversible reactions

As length of hydrocarbon chain increases, $K_{a}$ of carboxylic acid decreases as $-OH$ bond becomes less polar, hence proton is less able to be donated