You're right that these questions are basic stiochiometry
questions that should have been mastered at 'O' level. Fair enough,
you've an excuse that you didn't sit for 'O' level
Chem. But you must understand that it's unfeasible (ie. there are
limitations) to attempt to learn/teach stoichiometry (or chemistry
calculations in general) over the internet.
I'll leave it to current secondary school and JC students on
this forum to volunteer to offer you detailed worked
solutions (but try not to be dissapointed if no one
volunteers, coz doing the full worked solutions for stoichiometry
qns can be tedious).
I'll give brief guidance, without doing the detailed worked
solutions. If you don't even understand my guided steps (below),
then you should urgently seek additional help (eg. from teachers,
from peers who are doing well, from private tutors,
etc... understand that online help via forums like
this has its limitations).
Q1.
Determine moles of reactants 4-aminophenol and acetic
anhydride.
Based on stoichiometry, determine limiting and excess
reactants.
Based on moles of limiting reactant, calculate moles of
product.
Hence calculate theoretical sample mass of product.
% yield = experimental sample mass of product / theoretical
sample mass of product.
Q2.
Determine moles of salicyclic acid.
Apply stoichiometry to calculate theoretical moles of
product.
Hence calculate theoretical sample mass of product.
Since % yield is given as 75%, calculate experimental sample
mass of product.
Q3.
Write the balanced equation for the hydrolysis of boron
sulfide to generate boric acid and hydrogen sulfide.
Determine moles of reactants boron sulfide and water.
Based on stoichiometry, determine limiting and excess
reactants.
Calculate moles of excess reactant left unsed, hence calculate
sample mass of excess reactant left unsed.
Apply stoichiometry (based on limiting reactant) to calculate
moles of boric acid (product) generated.
Hence calculate sample mass of boric acid (product)
generated.
hi...i need some help here :)
q1.) paracetamol (C8H9NO2) is prepared from 4-aminophenol
(C6H7NO) and acetic anhydride (C4H6O3) according to the following
equation
C6H7NO (4-aminophenol) + C4H6O3 (acetic anhydride) ---->
C8H9NO2 (paracetamol) + C2H4O2 (acetic acid)
What is the percent yield of reaction if 100g of paracetamol is
produced from 109.2g of 4-aminophenol and 102.1g of acetic
anhydride?
q2.) Aspirin is produced from salicyclic acid (C7H6O3) and
acetic anhydride (C4H6O3) according to the following eqn
C7H6O3 (salicyclic acid) + C4H6O3 (acetic anhydride) ---->
C9H8O4 (aspirin) + C2H4O2 (acetic acid)
How many grams of aspirin would you obtain from 4.5g of
salicyclic acid of the reaction is 75%?
q3.) Boron sulphide (B2S3) reacts with water to form boric
acid (H3BO3) and hydrogen sulfide gas (H2S). Assume that 5.88g of
B2S3 is mized with 7.85g of water.
Which reactant is limiting and which reactant is in excess?
How many grams of the excess reactant are not consumed?
How many grams of boric acid are produced?
I know the qns seem introductory but i only have lower sec chem
knowledge..didnt take chem for my o levels..thks in advance!