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The half-life of a first order reaction is determined to be 85.5 years. How long will it take for the concentration of the reactant to reach 2% of its initial value?

At temperatures above 930 ∘C, PbO reduces PbS to form metallic lead (Pb). The byproduct of the reaction is SO2. Calculate the amount of lead produced (in kg) when a reactor is charged with 487.0 kg of PbS and 750 kg of PbO.

If the diffusivity is observed to double when the temperature is increased by 10 degrees C, what is

Nitrates are not tested forming a precipitate. Why not?

4.00g of lawn sand (a mixture of sand and ammonium sulphate) was weighed into a conical flask, and 25 cm3 of 2.0 mol dm-3 sodium hydroxide solution was pipetted into the same flask. The conical flask was boiled for 20 minutes, after which time all the ammonia had been driven off, because: (NH4) 2SO4 (s) + 2NaOH (aq) 2NH3 (g) + Na2SO4 (aq) + 2H2O (1) The residue in the flask was cooled and filtered to remove the sand. The filtrate containing unreacted NaOH was made up to 250 cm3 in a volumetric flask. 25 cm3 samples of this solution were titrated against 0.1 mol dm-3 hydrochloric acid using bromothymol blue as an indicator. HCl + NaOH  NaCl + H2O The mean titre was 20.0 cm3. Calculate the percentage of ammonium sulphate by mass in the lawn sand.

(6, 3c1) The bromide 13 can be transformed to cyclic compounds in the following reaction. Predict the major product 14 and briefly give your reasoning on how you arrive at your answer.

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