Which of the following equations are correctly balanced? i. agno3 + nabr → agbr + nano3 ii. al + o2 → al2o3 iii. caco3 → 3cao + co2 iv. cu2so4 + zn → znso4 + 2cu

i think it's I

I was confused by IV then search on gg and it said ZnSO4 should be Zn2SO4 instead but still im not sure Zn2SO4 is real

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: