Please tell me what I did wrong on these. (dS for formulas)?
Calculate ΔS in units of J/K for the following scenarios:
- Formation of 1 mole of HI(g) from its elements in their standard states:
Work:
( \text{H(g)} + \text{I(g)} \rightarrow \text{HI(g)} )
( \Delta S = (1 \, \text{mol HI} \times 206.33 \, \text{J/K}) - [(1 \, \text{mol H(g)} \times 114.60 \, \text{J/K}) + (1 \, \text{mol I(g)} \times 180.67 \, \text{J/K})] )
( \Delta S = -88.94 \, \text{J/K} )
- Formation of 1 mole of PCl(_5)(g) from the elements P(_4)(s, white) and Cl(_2)(g):
Work:
( \text{P}_4(\text{s}) + 10 \, \text{Cl}_2(\text{g}) \rightarrow 4 \, \text{PCl}_5(\text{g}) )
( \Delta S = (4 \, \text{mol PCl}_5 \times 4353 \, \text{J/K}) - [(1 \, \text{mol P}_4 \times 41.1 \, \text{J/K}) + (10 \, \text{mol Cl}_2 \times 1022.3 \, \text{J/K})] )
( \Delta S = -859 \, \text{J/K} )
- Reaction of exactly one mole of sulfur dioxide gas in a scrubbing process at 298 K:
Sulfur dioxide is released during the combustion of coal. Scrubbers remove much of the SO(_2) from flue gases by reacting it with lime slurries containing solid calcium hydroxide, forming solid calcium sulfite and liquid water. Calculate ( \Delta S ) in units of J/K for this reaction at 298 K.
Given: ( S^\circ ) of calcium sulfite(s) = ( 101.4 \, \text{J/mol·K} )
My Work:
( \text{SO}_2 + \text{calcium hydroxide} \rightarrow \text{CaSO}_3 + \text{H}_2\text{O} )
( \Delta S = [(1 \, \text{mol CaSO}_3 \times 107 \, \text{J/K}) + (1 \, \text{mol H}_2\text{O} \times 69.94 \, \text{J/K})] - [(1 \, \text{mol SO}_2 \times 248.1 \, \text{J/K}) + (1 \, \text{mol Ca(OH)}_2 \times 101.4 \, \text{J/K})] )
( \Delta S = -173 \, \text{J/K} )
Since the reaction occurs at 298 K, I assume that ( G = H - TS ) is not required for this calculation.
3 Answers
You might want to try to re-read the questions. You don't appear to be understanding what is written there. (I call it a brain ƒᴀʀт, but three out of 28 indicates a little lack of understanding)
If you have re-read the problems, then I offer the below:
You might want to go over your notes about what a mole is. It is an amount and a number. It is a fundamental conceptual building block for the study of chemistry.
It looks like you expect to be able to plug and chug on these. Which you can, once you start thinking in terms of atoms and molecules. Plugging and chugging BEFORE you understand what these little pieces are doing is a recipe for a C.
It IS the ATOMIC theory of matter, don't you know.
So, once you've absorbed that, re-read these three problems.
Still no joy? Read on, Gunga DIn
First H(g) is NOT the element's standard state! I thought everybody learned in grade school about H2 gas - the simplest molecule? Iodine, I leave to you (hint a gas???!!! not)
Second lets see you're making umpteen moles of something and calculate the dS. that was not the question. (hint: something about ONE mole)
Third read the problem. your chemical equation is from I don't know where but not from what is in the problem. (hint: products on the LEFT???)
I think different parenting styles can be effective but I tend to agree with Lynsey that some of the moms on here seem to be in an Attachment parenting sort if competition-who canʙʀᴇᴀsтfeed, cosleep, etc. the longest. Iʙʀᴇᴀsтfed for a year and hold my son alot but he also always slept in his own crib, and we did (gasp) let him cry a little bit when he was overtired and needed a sleep schedule which has been described as "child abuse" by many people on here. My mom and my female pediatrician who has 3 kids both told be schedules and routines make children feel happy and secure and it took me a while to learn this is the best advice out there. And honestly, I never really made him wait for much as an infant-but now that he is a toddler, and he wants to say try and get into something he knows is wrong I have to remind myself that I am the parent and that he is looking to me to teach him about the world and boundaries, even if that means carrying him off under my arm while he cries. I have noticed most of these meltdowns are pretty brief, because toddlers at least really do want some boundaries.
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