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Which statement correctly describes the relationship between reactant and yield? The actual yield is calculated from the amount of the excess reactant present. The actual yield is calculated from the amount of the limiting reactant present. The theoretical yield is calculated from the amount of the excess reactant present. The theoretical yield is calculated from the amount of the limiting reactant present.

Blair Lewis

in Chemistry

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Rodney Fox on January 31, 2019

Answer: the fourth stament, The theoretical yield is calculated from the amount of limiting reagent present.Justification:1) the Limiting reagent is the one that is in lesser proportion than the theoretical molar ratio.2) the Excess reagent is the one that is in greater proportion than the theoretical relationship.3) For example, if you have the equation a + 2B → C, means that 1 mol of A react with 2 moles of B to produce 1 mole of C. According to the equation, the theoretical molar ratio is 1 mol : 2 mol B : 1 moles of C. If the actual quantities of a and B were 2 and 4, respectively, were in the same ratio to the theoretical ratio, and all of the two reagents could react.But if, for example, 2 moles of reactant a and 2 mol of reactant B, only one of the moles of A could react with 2 moles of B, then B would be the limiting reagent: the whole of 2 moles of B would react, while only 1 mol of A reagent, and 1 mol of A would be more (A is in excess).Therefore, you may not use the 2 moles of a to calculate the theoretical yield (1 mol reacted), instead you must use the limiting reagent (B), which is the one that reacts completely.


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