Which of the following is a gas-evolution reaction?
a. 2 c2h6(l) + 7 o2(g) → 4 co2(g) + 6 h2o(g)
b. nh4cl(aq) + koh(aq) → kcl(aq) + nh3(g) + h2o(l) 2
c. h2(g) + o2(g) → 2 h2o(g)
d. licl(aq) + nano3(aq) → lino3(aq) + nacl(aq)
e. none of the above are gas-evolution reactions.

B. NH₄Cl(aq) + KOH(aq) → KCl(aq) + NH₃(g) + H₂O(l)

Explanation:

A gas-evolution reaction is defined as a chemical reaction that produce a gas and where reactants are not in gaseous phase.

Thus, the reactions:

A. 2C₂H₆(l) + 7O₂(g) → 4CO₂(g) + 6H₂O(g)  Is not a gas-evolution reaction because one reactant is a gas.

B. NH₄Cl(aq) + KOH(aq) → KCl(aq) + NH₃(g) + H₂O(l) Is a gas-evolution reaction because one product is the NH₃ that is a gas and reactants are not gases.

C. 2H₂(g) + O₂(g) → 2H₂O(g)  Is not a gas-evolution reaction because the reactants are gases

D. LiCl(aq) + NaNO₃(aq) → LiNO₃(aq) + NaCl(aq) Is not a gas-evolution reaction because there are not gases as products.

I hope it helps!

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:

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.