Which reaction is endothermic?
HCl + NaOH Right arrow. NaCl + H2O + 58 kJ
6CO2 + 12H2O + energy Right arrow. C6H12O6 + 6O2 + 6H2O
2Na + Cl2 Right arrow. 2NaCl + energy
2C2H6 + 7O2 Right arrow. 4CO2 + 6H2O + 2,502 kJ

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a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o