Two substances have the same molecular and empirical formulas.
Do...

Question

Two substances have the same molecular and empirical formulas.
Does this mean that they must be the same compound?

Accepted Answer

welcome back everyone in this example, we're told that substance A and substance B have the same empirical formula and molecular formula are the two substances the same. So we want to first recall what an empirical formula is and we should recall that an empirical formula is going to be the simplest whole number ratio of our elements in our compound. And so for example we would have something like C. 02 or H 20. Or we can say N. 02 versus our molecular formula we would recall is going to be the actual whole number ratio of our elements in a compound and we'll just make this go down for some more room here. And so for example, That could be again c. 0 2. We could have something like N where we can see that we have that simplified ratio of N. 02 where we have two atoms of oxygen for one atom of nitrogen. So now that we have distinguished molecular formulas from empirical formulas, we want to next recall something known as an specifically structural members. And we want to recall that structural items have these same atoms but different arrangement of bonding, I'm sorry, different arrangement of bonding the atoms. And so for example, we could be given a molecular formula of something like C two H 60. Which we can make the below possible structures where we have A Methyl group on one end. So recall that metal is CH three. Then we have that bonded to a carbon bonded to two other hydrogen and then we have our hydroxide group or alcohol group. And we can recognize this molecule or the structure as ethanol, whereas we can take this same molecular formula and have a following arrangement where we have one methyl group on one end in the middle, we have an oxygen atom and then surrounding that oxygen atom we have another metal group or a second metal group on the other side. And so we can recognize this structural arrangement as the compound dimethyl ether, meaning that these are two different compounds, but they're made from the same molecular formula. So based on the prompt our substance A and substance be the same even though they have the same empirical and molecular formula based on what we've outlined, we can say that no the substance or we can say no substance A and B. Are likely ice climbers of different substances. And so this would be our final answer to complete this example. And this will correspond to choice. Be in the multiple choice. I hope that everything I reviewed was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video

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