Reversible Reactions Flashcards
what are reversible reactions?
reactions that can go backwards as well as forwards
what does this symbol mean: ⇌
that a reaction is reversible
in the decomposition of N2O4 to form NO2, what is the colour change?
N2O4(g) - colourless ⇌ 2NO2(g) - brown
what does a reversible reaction depend on?
the amounts of reactants and products and the conditions such as temperature and pressure
how does decomposition of N2O4 to form NO2 go forwards?
under high pressure
how does decomposition of N2O4 to form NO2 go backwards?
at low temperatures
what does the enthalpy change (ΔH) for a reversible reaction refer to?
the forward reaction - for the backwards reaction ΔH is the same number with the opposite sign
is the dehydration of copper sulfate a reversible reaction?
yes
how do you make the reaction go forwards in the dehydration of copper sulfate crystals?
you heat the hydrated copper sulfate crystals - the crystals turn from blue to white as they lose all their water
how do you make the reaction go backwards in the dehydration of copper sulfate crystals?
you add water to anhydrous copper sulfate - the white powder absorbs the water and turns blue in the process
is the decomposition of ammonium chloride a reversible reaction?
yes
how do you make the reaction go forwards in the thermal decomposition of ammonium chloride?
you heat the ammonium chloride - nothing appears to change because NH3 and HCl are both colourless gases
how do you make the reaction go backwards in the decomposition of ammonium chloride?
you allow NH3(g) and HCl (g) to mix in the absence of heat - white NH4Cl
how can the decomposition of ammonium chloride be demonstrated?
- by gently heating NH4Cl in a test tube
- the NH4Cl at the bottom of the tube decomposes to form invisible NH3 and HCl
- the invisible NH3 and HCl cool as they move up the tube, recombining to form NH4Cl
