The Correct answer to this question for Penn Foster Students is: 137.5 m
b. element
c. molecule
d. compound
Answer:
A) Solution
Explanation:
A solution is not a pure substance, while elements, molecules, and compounds are examples of pure substances. The correct option is A.
The correct answer is a. solution. A solution is a mixture of two or more substances, so it is not a pure substance. Examples of solutions include saltwater and sugar water. On the other hand, elements, molecules, and compounds are all examples of pure substances. An element is a substance that cannot be broken down into simpler substances, such as gold or oxygen. A molecule is a combination of two or more atoms held together by chemical bonds, like water (H₂O) or carbon dioxide (CO₂). Lastly, a compound is a substance made up of two or more different elements chemically bonded together, like table salt (NaCl) or water (H₂O).
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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.
Answer: the fourth stament, The theoretical yield is calculated from the amount of the limiting reactant present.
Justification:
1) Limiting reactant is the one that is in less proportion than the theoretical mole ratio.
2) Excess reactant is the one that is in greater proportion than the theoretical ratio.
3) For example, if you have the equation A + 2B → C, means that 1 mol of A react with 2 moles of B to yield 1 mol of C.
As per that equation, the theoretical mole ratio is 1 mol of A : 2 moles of B : 1 moles of C.
If the actual amounts of A and B were 2 and 4, respectively, they were in the same ratio as the theoretical ratio, and all of the both reactants could react.
But if you had, for example, 2 moles of reactant A and 2 moles of reactant B, only one of the moles of A could react with the 2 moles of B, so B would be the limiting reactant: the whole 2 moles of B would react, while only 1 mole of A would reactant, and 1 mole of A would be left over (A is in excess).
Therefore, you cannot use the 2 moles of A to calculate the theoretical yield (since only 1 mole reacted), instead you must use the limiting reactant (B), which is the one that reacts completely.