ASAP stands for as soon as possible
Moles = mass/molar mass, so n(C2H6O)= 16.0 / (12+12+(1x6)+16)
=0.348 (to correct sig figs)
M{(NH₄)₂Cr₂O₇}=2A(N)+8A(H)+2A(Cr)+7A(O)
M{(NH₄)₂Cr₂O₇}=252.065 g/mol
M(Cr)=51.996 g/mol
m{(NH₄)₂Cr₂O₇}/M{(NH₄)₂Cr₂O₇}=m(Cr)/2M(Cr)
m(Cr)=2M(Cr)m{(NH₄)₂Cr₂O₇}/M{(NH₄)₂Cr₂O₇}
m(Cr)=2*51.996*35.8/252.065=14.770 g
m(Cr)=14.770 g
In this redox reaction, the Cu goes from oxidation state of (0) to (+2), therefore it oxidises. N in HNO₃ goes from oxidation state of (+5) to N in NO with oxidation state of (+2) and becomes reduced.
Cu acts as the reducing reagent and HNO₃ is the oxidising agent.
oxidation half reaction
Cu ---> Cu²⁺ + 2e --1)
reduction half reaction
4H⁺ + 3e + NO₃⁻ ---> NO + 2H₂O --2)
to balance the number of electrons , 1) x3 and 2) x2
3Cu ---> 3Cu²⁺ + 6e
8H⁺ + 6e + 2NO₃⁻ ---> 2NO + 4H₂O
add the 2 equations
3Cu + 8H⁺ + 2NO₃⁻ ---> 3Cu²⁺ + 2NO + 4H₂O
add 6 nitrate ions to both sides to add up to 8 and form acid with 8H⁺ ions
3Cu + 8HNO₃ ---> 3Cu(NO₃)₂ + 2NO + 4H₂O
Balanced equation for the redox reaction is as follows;
3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 2NO(g) + 4H₂O<span>(l)
NO has a coefficient of 2
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