Answer:
ΔG°rxn = -69.0 kJ
Explanation:
Let's consider the following thermochemical equation.
N₂O(g) + NO₂(g) → 3 NO(g) ΔG°rxn = -23.0 kJ
Since ΔG°rxn < 0, this reaction is exergonic, that is, 23.0 kJ of energy are released. The Gibbs free energy is an extensive property, meaning that it depends on the amount of matter. Then, if we multiply the amount of matter by 3 (by multiplying the stoichiometric coefficients by 3), the ΔG°rxn will also be tripled.
3 N₂O(g) + 3 NO₂(g) → 9 NO(g) ΔG°rxn = -69.0 kJ
There are 3 significant figures. Significant numbers are the numbers that build up your total number. 1-9 always count, 0 only counts if it’s after another number. For example: 0,901 has 3 significant numbers as does 0,910. 9,10 also has 3. 0,09 has just 1.
They were natural philosophers that used experimentation to establish the cause effect relations and explanations, in an epoque when many "theories' were not supported by experiments but by some authority (antique philosophers like Aristoteles or the Catholic Church).
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
Fe(NO3)2=0
Fe+2(+3+3*-2)=0
Fe+2*-3=0
Fe=-(-6)
Fe=+6
So, Fe=+6, N=+3, O=-2