april 2024 chemistry revision Flashcards
Endothermic reactions are [hotter/colder] than their surrounding environment
Endothermic reactions are colder than their surrounding environment.
Exothermic reactions are [hotter/colder] than their surrounding environment
Exothermic reactions are hotter than their surrounding environment
Give 3 examples of an endothermic reaction
photosynthesis, evaporation, thermal decomposition etc
Give 3 examples of an exothermic reaction
combustion, neutralisation, deposition of dry ice, respiration, solution of sulphuric acid into water, oxidisation, etc
How do we tell whether a reaction is endothermic or exothermic?
We can tell by the temperature change.
The reaction is [endothermic/exothermic] if its temperature has increased.
The reaction is exothermic if its temperature has increased.
The reaction is [exothermic/endothermic] if its temperature has decreased.
The reaction is endothermic if its temperature has decreased.
what do we use to measure energy changes in a reaction?
a calorimeter
Why do we use an insulated cup when measuring energy changes?
To prevent heat loss - to make sure the results are accurate.
Give a brief summary of the method we would use to measure an energy change.
- record the starting temperature
- record the end temperature
- repeat and find the average of both
- calculate- temperature change = start temp - end temp
Define the term ‘activation energy’
The minimum amount of energy reactant particles need in order to collide and react.
in an exothermic reaction, the energy of the products is [more/less] than the energy of the reactants.
in an exothermic reaction, the energy of the products is less than the energy of the reactants.
in an endothermic reaction, the energy of the products is [more/less] than the energy of the reactants.
in an endothermic reaction, the energy of the products is more than the energy of the reactants.
what do neutralisation reactions produce?
a salt + water
stronger acids have a [lower/higher] pH.
stronger acids have a lower pH.
a strong acid will [fully/only partially] ionize because it has a [lower/higher] concentration of H+ ions.
a strong acid will fully ionize because it has a higher concentration of H+ ions.
a weak acid will [fully/only partially] ionize
a weak acid will only partially ionize.
metal oxides produce _______ + _________
metal oxides produce salt + water
metal hydroxides produce _______ + _________
metal hydroxides produce salt + water
metal carbonates produce _______+________
metal carbonates produce salt + water + carbon dioxide.
what number is neutral on the pH scale?
7
the colours for acids range from ____ to ______.
the colours for acids range from red to yellow.
the colours for alkalis range from _____ to ______.
the colours for alkalis range from blue to purple.
hydrochloric acid (HCl) + sodium oxide (Na2O) ——-> ________+________
hydrochloric acid (HCl) + sodium oxide (Na2O) ——-> NaCl + H2O
H2SO4 + KOH ——–> ______ + _______
H2SO4 + KOH ——–> K2SO4 + H2O
What is an acid?
a substance that forms aqueous solutions with pH less than 7.
What is a base?
any substance with a pH more than 7.
What is an alkali?
a base that is soluble in water.
alkalis form [Oh- / H+] ions in water which we call _________.
alkalis form Oh- ions in water which we call hydroxide ions.
acids ionize in aqueous solutions to release [Oh- / H+] ions, which means they split or dissociate into their ions.
acids ionize in aqueous solutions to release H+ ions, which means they split or dissociate into their ions.
the ionization of a weak acid is reversible, which means…?
… there is an equilibrium dissociated and undissociated forms of acid.
the pH scale is a measure of…?
the pH scale is a measure of how acidic or alkaline a solution is.
for acids, what is the definition of ‘strength’ ?
Strength means how much an acid dissociates.
for acids, what is the definition of concentration?
Concentration means how much acid there is in a certain solution.
