sig figs

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sig figs

Postby 705121606 » Mon Jan 27, 2020 4:45 pm

"piston confines 0.250 mol He to 1.50L at 25C [...] the gas is able to expand through additional 1.20L against constant pressure of 1atm." The answer had 3 sig figs. I read the sig fig worksheet on Dr. Lavelle's website but I am still confused. What part of the question counts for sig figs and what doesn't?

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Re: sig figs

Postby romina_4C » Mon Jan 27, 2020 4:55 pm

Usually in cases like these, since 25 degrees celsius and 1 atm are constants and taken just as constants in the surroundings, you take into account the sig figs for the values that change (moles and liters), thus it being 3.

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Re: sig figs

Postby BCaballero_4F » Mon Jan 27, 2020 5:53 pm

Moles and liters count for sig figs in this question

Juliana Chopelas 1A
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Re: sig figs

Postby Juliana Chopelas 1A » Mon Jan 27, 2020 9:00 pm

Moles and liters count for the sig figs that is why there are 3 of them

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Re: sig figs

Postby Isha_Maniyar_Dis2E » Mon Jan 27, 2020 9:04 pm

For questions with constants such as the 1 atm and 25 degrees Celsius, you do not consider these in determining sig figs. A good tip is to just follow the sig figs in the number given in the problem (molar amount, liters, etc). However, when calculating your answer, keep a lot of decimal places so you can get a very accurate calculation. Only simplify in the last step, when you are providing the final answer.

Hope this helped!

Mitchell Koss 4G
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Re: sig figs

Postby Mitchell Koss 4G » Mon Jan 27, 2020 10:09 pm

The only deviation for standard sig fig rules is pH and logs.

Maya Beal Dis 1D
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Re: sig figs

Postby Maya Beal Dis 1D » Wed Jan 29, 2020 3:36 pm

When adding and subtracting you round to the value place of whichever component has the largest value for it's significant figures, where in multiplication and division you count the number of significant figures and ignore their place values.

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