Acid and base Flashcards
how to dry a solid from aq solution
- filter the mixture
- wash it with DI water
- dry in oven
what is standard solution
solutions with accurately known concentrations
use to determine concentrations of other reagent
why back titration is needed
no suitable indicator
reaction rate is slow
insoluble in water
why its not appropriate to rinse the conical flask with acid
Some H+ ions remain in the flask, and more alkali than actually required is used to reach the titration end point.
how to prepare a 250cm3 of standard solution
to dissolve the solid by adding deionized water to the solid in a beaker
Transfer the solution with rinsing with deionized water into a 250cm3 volumetric flask and add deionized water until the lower meniscus of water level reaches the graduation mark of the flask.
Shake thoroughly.
how to perform crystallisation
Evaporate the filtrate, allow solid crystallize out
Collect crystals and then dry it with a filter paper.
what is alkali
Alkali is water soluble substance reacts with acid to give salt and water only
is all acidic compound contain H?
no
acidic =/= acid
CO2 SO2 is acidic
what is titrant analyte and titre
titrant in burette
analyte in conical flask
titre is the volume/concentration of the solution determined
NH4Cl acidic or alkaline?
acidic
XHSO4 acidic or alkaline?
acidic
is NaOH/ Na2O a salt
no
OH- and O2- are not come from anion of any acid
salt = metal cation or NH4+ + anion formed from acid
what is basicity?
basicity of an acid is the maximum number of H+ ion which can be produced from 1 acid molecule / the number of ionizable H atom in one acid molecule
what shd be done when conc acid spill to the skin
wash it with running cold water
how to dilute a conc acid
add conc acid slowly to a large amount of water with constant stirring
if water is added to conc acid, a lot of heat is released and the heat can cause splashing out of the corrosive acid solution.
difference between drying agent and dehydrating agent
drying agent –> physical change (CaO / anhydrous CaCl2)
dehydrating agent –> chemical change (conc H2SO4)
which gas does anhydrous CaCl2 cannot dry
NH3
why use an inverted funnel when passing HCl gas to water
prevent sucking back of water as HCl is soluble in water
Na2SO3 acidic or alkaline?
alkaline
NaHSO3 acidic or alkaline?
alkaline
why theres no observable change when Ca2+ + NH3
OH- concentration too low in NH3
why the boiling tube should be tilted downward in an experiment
prevent the condensed water from flowing back into the hot boilng tube which would cause cracking of the tube
how NH3 can be collected
upward delivery as NH3 is less dense than air
or gas syringe (百搭）
why cant we use acid when alkali spill to our skin
neutralization is highly exothermic
it causes burning of our skin
what does the strength of acid depends on?
the degree of ionization to form H+
what does the strength of alkali depends on?
the degree of ionization to form OH-
factors that affect the pH of an aicd
concentration
strength (strong or weak)
basicity
why some soil is acidic
acid rain
acidic fertiliser
what can be used to neutralise acidic soil
CaO CaOH CaCO3
as they are not very soluble in water
so it wont make the soil too alkaline
why nitrogen is present in fertiliser
nitrogen is required for the formation of amino acid
why we should wash the salt prepared with cold DI water
to remove any soluble impurity
help reduce the loss of the salt
what is volumetric analysis
its a method used to determine quantity or concentration of a substance by titration
what is requirement of primary standard
highly pure
stable in air and solution
does not absorb water or carbon dioxide in air
why conc H2SO4 cant be primary standard
it absorb water so it cannot weigh out accurately
how to prepare a primary standard
from a solid
from diluting a more concentrated standard solution
titration of solution A against solution B
A or B in burette?
B in burette
A in conical flask
burette must hold
strong acid/ strong alkali
how the end point between the neutralization of weak acid and weak alkali be determined
measuring the temperature change and plot a graph
why diluting chemical in titration
to save chemicals
what is the state of citric acid in room temperature
solid
describe the procedure that should be followed when preparing a burette containing HCl
rinse the burette with distilled water
then with the hydrochloric acid
fill the burette with the hydrochloric acid, making sure that the space between the tap and the tip of the burette is filled with the acid so there is no air bubbles in the burette
Also, the meniscus should not be above the zero mark
