50 points + brainliest to whoever is right

which of the following is not true about percent yield?
percent yield is often less than 100%
percent yields measures the efficiency of a reaction carried out in a lab
percent yield of 100% is unlikely when reactants or products were no carefully measured
percent yield is the ratio of theoretical yield to actual yield expressed as a percent

The identities of substances are the same before and after which type of change

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.

Consider the following unbalanced equation for the combustion of hexane: αc6h14(g)+βo2(g)→γco2(g)+δh2o(g) part a balance the equation. give your answer as an ordered set of numbers α, β, γ, use the least possible integers for the coefficients. α α , β, γ, δ = nothing request answer part b determine how many moles of o2 are required to react completely with 5.6 moles c6h14. express your answer using two significant figures. n n = nothing mol request answer provide feedback