## sig figs

705121606
Posts: 68
Joined: Wed Sep 18, 2019 12:17 am

### sig figs

"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?

romina_4C
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

### Re: sig figs

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.

BCaballero_4F
Posts: 94
Joined: Wed Nov 14, 2018 12:22 am

### Re: sig figs

Moles and liters count for sig figs in this question

Juliana Chopelas 1A
Posts: 50
Joined: Sat Aug 24, 2019 12:16 am

### Re: sig figs

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

Isha_Maniyar_Dis2E
Posts: 110
Joined: Thu Jul 11, 2019 12:16 am

### Re: sig figs

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
Posts: 128
Joined: Sat Jul 20, 2019 12:17 am

### Re: sig figs

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

Maya Beal Dis 1D
Posts: 100
Joined: Sat Aug 17, 2019 12:16 am
Been upvoted: 2 times

### Re: sig figs

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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