Empirical and Molecular Formulas

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jordanginyard_
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Empirical and Molecular Formulas

Postby jordanginyard_ » Sun Oct 11, 2020 11:46 pm

On the lecture video on the chem 14A website, it said that the molecular formula must be the same for empirical. However, I don't know if that is true because isn't the empirical formula the relative and like the molecular formula is the multiple of empirical.

Sophia Hu 1A
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Re: Empirical and Molecular Formulas

Postby Sophia Hu 1A » Mon Oct 12, 2020 7:32 am

Th empirical formula is the relative number of atoms, it is a ratio. The molecular formula is the actual number of atoms, and like you said it is a multiple of the empirical formula. The empirical formula can be the molecular formula where the molecular formula is a multiple of 1 of the empirical formula. You can think about how we always divide the molecular mass by the empirical formula to find the multiple to multiply the empirical formula by. If the empirical formula is the molecular formula, then this multiple will be 1. However, this is not always the case. This only occurs if the molar mass of the empirical formula equals the molar mass of the molecular formula typically given in the problem.

Samudrala_Vaishnavi 3A
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Re: Empirical and Molecular Formulas

Postby Samudrala_Vaishnavi 3A » Tue Oct 13, 2020 8:31 am

I don't think the website meant the exact "same thing". You're right, the empirical formula is the relative number (ratio) of atoms per element and the molecular formula is the exact number of the atoms in the context of the actual balanced equation or experiment in a lab. However, they are SIMILAR considering that the ratios are the same between them. For instance, lets look at glucose. Its empirical formula is CH20 or is a 1:2:1 ratio. So, is we multiply by six, we get the same ratio C6H12O6, 6:12:6, 1:2:1. C6H12O6 is the molecular formula for glucose.

Natalie Do 3F
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Re: Empirical and Molecular Formulas

Postby Natalie Do 3F » Fri Oct 16, 2020 3:47 pm

Basically think of the empirical formula as simplifying the molecular formula as you would a fraction. If the ratio is 2:4:8, they have greatest common factor of 2 so you divide them all by 2 to get 1:2:4.

Sophia Spungin 2E
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Re: Empirical and Molecular Formulas

Postby Sophia Spungin 2E » Fri Oct 16, 2020 4:13 pm

The ratios of elements are the same, however, the multiples are different. Empirical equations are the simplest, whole number ratios of atoms, whereas Molecular formulas take into account the compound's molar mass and appear as a multiple of the empirical formula. These formulas can be the same if the molar mass of the empirical formula matches the molar mass of the compound in question!

lwon Dis2I
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Re: Empirical and Molecular Formulas

Postby lwon Dis2I » Fri Oct 16, 2020 9:38 pm

How would you solve this?

In the following ball-and-stick molecular structures, dark gray indicates carbon; white, hydrogen; blue, nitrogen; and green, chlorine. Write the empirical and molecular formulas of each structure. Hint: It may be easier to write the molecular formula first.
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Juliana Rosales 1H
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Re: Empirical and Molecular Formulas

Postby Juliana Rosales 1H » Sun Oct 25, 2020 11:52 pm

Basically, the ratios are the same for the molecular and the empirical formulas.if they are not something is wrong.

Daniela Santana 2L
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Re: Empirical and Molecular Formulas

Postby Daniela Santana 2L » Sun Oct 25, 2020 11:53 pm

Hi, yes the empirical formula shows the relative number of atoms in a molecule. It is a ratio of the molecular formula. The molecular formula shows the actual number of atoms in the molecule. The empirical and molecular formula relate to one another and you can find a factor between the two and use it to solve for them.

Daniela Santana 2L
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Joined: Wed Sep 30, 2020 9:59 pm

Re: Empirical and Molecular Formulas

Postby Daniela Santana 2L » Sun Oct 25, 2020 11:58 pm

lwong Dis1L wrote:How would you solve this?

In the following ball-and-stick molecular structures, dark gray indicates carbon; white, hydrogen; blue, nitrogen; and green, chlorine. Write the empirical and molecular formulas of each structure. Hint: It may be easier to write the molecular formula first.


Hi, you would solve this problem by counting each of the balls in each structure and separating them based on which element they are. (the problem tells you which color represents which element). This is the molecular formula. In order to get the empirical formula you would have to simplify the molecular formula to the smallest ratio you can get since the molecular formula is just a multiple of the empirical formula. I struggled with this problem too. Hope this explanation helped!

Cassidy Cheng 1J
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Re: Empirical and Molecular Formulas

Postby Cassidy Cheng 1J » Mon Oct 26, 2020 8:53 am

Yeah, like the previous commenters said, the molecular formula is a factor of the empirical formula. However, the molecular formula *could* be the same as the empirical formula if the ratio between them is 1:1.


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