Significant Figures of 225.0 & Molar Volume at STP

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Discussion Overview

The discussion revolves around the determination of significant figures in the number 225.0 and the consideration of significant figures in the molar volume of a gas at standard temperature and pressure (STP). It includes aspects of theoretical understanding and practical application in calculations.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant asserts that 225.0 has 4 significant figures, while another claims it has 3, leading to a disagreement regarding the interpretation of significant figures.
  • Another participant supports the view that trailing zeros to the right of the decimal are significant, suggesting that the initial participant's understanding is correct.
  • A further contribution questions the inclusion of the trailing zero, implying that it may depend on the context of how the number was derived, particularly if it was rounded from a more precise value.
  • Regarding molar volume at STP, one participant explains that the ideal gas equation allows for the calculation of molar volume with infinite accuracy due to the defined nature of constants involved, although this was not always the case historically.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the number of significant figures in 225.0, with multiple competing views presented. The discussion on molar volume at STP introduces additional complexity without resolving the earlier disagreement.

Contextual Notes

Participants reference the significance of trailing zeros and the historical context of the ideal gas constant, indicating that assumptions about significant figures may depend on the specific context of calculations and definitions used.

i_love_science
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What are the number of significant figures of 225.0? I think it is 4, but the solution says it's 3.

Also, is the significant figures of molar volume at STP (22.7 L/mol) considered? Thanks.
 
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A super-duper quick Google (which doesn't count here) agrees with my understanding:
  • Trailing zeros to the right of the decimal ARE significant. ...
  • Trailing zeros in a whole number with the decimal shown ARE significant.
That suggests you are right. I'd take it up with your instructor.
 
225.0 has four significant figures. Why did you include the zero in your answer? Did you round it from something like, 225.0173946289?
It sounds like it was part of a calculation and unless we see that calculation, we can’t tell you what is correct!
 
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Molar volume of gas at STP can be calculated from the ideal gas equation. As of today all numbers in that equation - including R, ideal gas constant - are defined, that is, they have infinite number of significant digits (you can put as many zeros at the end as you need). That means it is possible to calculate molar volume with infinite accuracy.

It wasn't always this way, R used to be a measured quantity, with known experimental error.
 

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