http://zh.sgforums.com/forums/2297/topics/313906 zh-CN 60 <p><img src="/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /><img src= "/images/emoticons/classic/icon_rolleyes.gif" alt= "icon_rolleyes.gif" /></p> Sat, 12 Apr 2008 16:33:09 +0800 zh.sgforums.com:2297:313906:8007138 FirePig http://zh.sgforums.com/forums/2297/topics/313906 <p>hmm im not sure for part c... i keep hitting a wall... will redo tonight.. still soo tired from last night</p> Sat, 12 Apr 2008 10:46:02 +0800 zh.sgforums.com:2297:313906:8006419 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by eagle:</div> <div class="quote_body"> <p>C19 P61</p> <p>a) <img src= "http://upload.wikimedia.org/math/3/1/3/313fe136a3be00240aa1db83a2b45bb0.png" height="17" alt="" width="142" /></p> <p>1.8 * 176^y = 5.51 * 79.2^y<br /> 2.2222^y = 3.061111<br /> y = ln(3.061111) / ln(2.222222) = 1.4</p> <p>=&gt; diatomic gas</p> <p>b) <img src= "http://upload.wikimedia.org/math/d/1/4/d14ee89475a402cb824558b3cc5c6c9d.png" height="20" alt="" width="158" /></p> <p>so,<br /> 310 * 176^1.4 = T * 79.2^1.4<br /> T = 948.1K</p> <p>c) PV = nRT<br /> so n = PV/RT<br /> p = 1.80atm, 1 atm = 101325 Pa<br /> V = 176L = 176000cm3 = 0.176 m3<br /> R = 8.314 J·K⁻¹mol^-1<br /> T = 310K</p> <p>thus, n = 6.92 mol</p> </div> </blockquote> <p>Part b careless.... Equation is still correct... Anyway you should also help check for careless mistake mah... Not just take the values and use them without trying to understand how the equation was used...</p> <p>The power should be 0.4, not 1.4</p> <p>310 * 176^0.4 = T * 79.2^0.4<br /> T = 426.65K</p> <p>&nbsp;</p> <p>Part c is already ideal gas equation. Maybe you could help check if the calculations are wrong...</p> Fri, 11 Apr 2008 18:50:13 +0800 zh.sgforums.com:2297:313906:8005184 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>b and c cant get correct...hint is to apply the ideal gas law. anyways cant reply tonight..&nbsp;</p> Fri, 11 Apr 2008 15:15:47 +0800 zh.sgforums.com:2297:313906:8004721 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>C19 P61</p> <p>a) <img src= "http://upload.wikimedia.org/math/3/1/3/313fe136a3be00240aa1db83a2b45bb0.png" height="17" alt="" width="142" /></p> <p>1.8 * 176^y = 5.51 * 79.2^y<br /> 2.2222^y = 3.061111<br /> y = ln(3.061111) / ln(2.222222) = 1.4</p> <p>=&gt; diatomic gas</p> <p>b) <img src= "http://upload.wikimedia.org/math/d/1/4/d14ee89475a402cb824558b3cc5c6c9d.png" height="20" alt="" width="158" /></p> <p>so,<br /> 310 * 176^1.4 = T * 79.2^1.4<br /> T = 948.1K</p> <p>c) PV = nRT<br /> so n = PV/RT<br /> p = 1.80atm, 1 atm = 101325 Pa<br /> V = 176L = 176000cm3 = 0.176 m3<br /> R = 8.314 J·K⁻¹mol^-1<br /> T = 310K</p> <p>thus, n = 6.92 mol</p> Fri, 11 Apr 2008 11:44:44 +0800 zh.sgforums.com:2297:313906:8004227 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>thanks, that's the correct answer ^^</p> Fri, 11 Apr 2008 07:08:29 +0800 zh.sgforums.com:2297:313906:8003868 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>C19 P43</p> <p>a) 0J as volume didn't change</p> <p>b) <img src= "http://upload.wikimedia.org/math/f/4/7/f4770f656f6c654810143bc7f07aaf16.png" height="41" alt="" width="190" /></p> <p>change in T = 16.3<br /> N = 2.42 mol<br /> f = degree of freedom = 3 for monoatomic gas<br /> k = boltzmann constant</p> <p>change in thermal energy = 491.7 J =&gt; not confirmed</p> <p>c) <img src= "http://upload.wikimedia.org/math/0/d/f/0df7e93c5d3ab53772c0e27472397e03.png" height="21" alt="" width="166" /></p> <p>change in internal energy = a) + b) = 491.7J</p> <p>d) should be 491.7J / (2.42 * 1mol) = 3.37e-22 J</p> Thu, 10 Apr 2008 22:54:09 +0800 zh.sgforums.com:2297:313906:8003109 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>apologize for being so careless :(</p> Thu, 10 Apr 2008 22:40:02 +0800 zh.sgforums.com:2297:313906:8003069 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>4.71 is the correct answer! XD</p> Thu, 10 Apr 2008 22:05:48 +0800 zh.sgforums.com:2297:313906:8002914 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>OH!!!!!! SORRY.... didn't see it is Vavg!</p> <p>According to your equations,</p> <p>Vrms2 = Vavg * sqrt (3 * pi / 8) = 2.171 Vrms1</p> <p>So should be 2.171^2 = 4.71?</p> <p>&nbsp;</p> Thu, 10 Apr 2008 21:49:51 +0800 zh.sgforums.com:2297:313906:8002867 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>arrr....</p> <p>use Vavg and Vrms equations and rearrange to get m1/m2 ratio</p> <p>thats how someone else got it &gt;__&lt; but how :O</p> Thu, 10 Apr 2008 21:46:05 +0800 zh.sgforums.com:2297:313906:8002857 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>With this formula<br /> p = (nMv^2)/3V</p> <p>pV/n = Mv^2 / 3</p> <p>this is a constant because R and T are constants here</p> <p>so,</p> <p>m1v1^2 / 3 = m2v2^2 / 3</p> <p>Ratio of m1/m2 is still 4 leh...</p> <p>&nbsp;</p> <p>I think different p means different V or n only... The Vrms is still heavily dependent on temperature.</p> Thu, 10 Apr 2008 21:32:55 +0800 zh.sgforums.com:2297:313906:8002826 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>i think that's related to the value "R"</p> <p>&nbsp;</p> <p>ps: 4 isnt the ans</p> Thu, 10 Apr 2008 21:25:46 +0800 zh.sgforums.com:2297:313906:8002810 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by eagle:</div> <div class="quote_body"> <p>C19 P38</p> <p>temperature the same, kinetic energy of molecules should be the same</p> <p>thus, (0.5)(m1)(v1) = (0.5)(m2)(v2)</p> <p>but v2 = 2v1,</p> <p>m1/m2 = v2/v1 = 2</p> <p>&nbsp;</p> <p>Not confirmed though....</p> </div> </blockquote> <p>Oops... Careless with the above formula... Should be 1/2 m v^2</p> <p>(0.5)(m1)(v1)^2 = (0.5)(m2)(v2)^2</p> <p>but v2 = 2v1,</p> <p>m1/m2 = (v2/v1)^2 = 4</p> Thu, 10 Apr 2008 21:13:10 +0800 zh.sgforums.com:2297:313906:8002776 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>that's O level chemistry I think...</p> <p>molar mass = molecular mass * mole number</p> Thu, 10 Apr 2008 21:10:39 +0800 zh.sgforums.com:2297:313906:8002773 eagle http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by eagle:</div> <div class="quote_body"> <p>C19 P38</p> <p>temperature the same, kinetic energy of molecules should be the same</p> <p>thus, (0.5)(m1)(v1) = (0.5)(m2)(v2)</p> <p>but v2 = 2v1,</p> <p>m1/m2 = v2/v1 = 2</p> <p>&nbsp;</p> <p>Not confirmed though....</p> </div> </blockquote> <p>ahh i have a hint:x</p> <p>&nbsp;</p> <p>You do not need all the information given. Did you write the equations for average speed and rms speed? How is molar mass related to molecular mass?</p> Thu, 10 Apr 2008 20:42:18 +0800 zh.sgforums.com:2297:313906:8002713 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>looking at some formula...</p> <p>&nbsp;</p> <p>p = (nMv^2)/3V , with v = root mean square speed</p> <p>v(rms) = Sq root of (3RT/M)</p> <p>&nbsp;</p> <p>V(avg) is top line of : <img src= "http://edugen.wiley.com/edugen/courses/crs1650/art/math/halliday8019c19/math098.gif" height="98" alt="" width="263" /></p> <p>&nbsp;</p> Thu, 10 Apr 2008 20:41:05 +0800 zh.sgforums.com:2297:313906:8002709 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>nah 2 isnt the answer... there must be a reason why 5p is there</p> Thu, 10 Apr 2008 20:39:08 +0800 zh.sgforums.com:2297:313906:8002703 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <p>C19 P38</p> <p>temperature the same, kinetic energy of molecules should be the same</p> <p>thus, (0.5)(m1)(v1) = (0.5)(m2)(v2)</p> <p>but v2 = 2v1,</p> <p>m1/m2 = v2/v1 = 2</p> <p>&nbsp;</p> <p>Not confirmed though....</p> Thu, 10 Apr 2008 20:37:05 +0800 zh.sgforums.com:2297:313906:8002696 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>I think I forgot all the formulas &gt;_&lt;</p> Thu, 10 Apr 2008 20:27:40 +0800 zh.sgforums.com:2297:313906:8002676 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>it's umm...</p> <p>&nbsp;</p> <p>&nbsp;</p> <p>... kinda &gt;_&lt;</p> <p>&nbsp;</p> <p>&nbsp;</p> <p>the other questions are soooo argh</p> Thu, 10 Apr 2008 20:24:05 +0800 zh.sgforums.com:2297:313906:8002672 WoAiMeiMei http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by weewee:</div> <div class="quote_body"> <p>I am so ashamed to say i have never heard of this formula. Is this A level physics?</p> </div> </blockquote> <p>Uni Year 1 engineering physics...</p> <p>&nbsp;</p> <p>btw, are all the questions solved already?</p> Thu, 10 Apr 2008 20:24:00 +0800 zh.sgforums.com:2297:313906:8002671 eagle http://zh.sgforums.com/forums/2297/topics/313906 <p>I am so ashamed to say i have never heard of this formula. Is this A level physics?</p> Thu, 10 Apr 2008 19:39:19 +0800 zh.sgforums.com:2297:313906:8002542 weewee http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by weewee:</div> <div class="quote_body"> <p><br /> Yeah as i state, i dunno the formula. TS's formula is wrong in #1 post.</p> </div> </blockquote> <p><br /> orh. paiseh. &gt;&lt;</p> Thu, 10 Apr 2008 19:34:58 +0800 zh.sgforums.com:2297:313906:8002522 ^tamago^ http://zh.sgforums.com/forums/2297/topics/313906 <blockquote> <div class="quote_from">Originally posted by ^tamago^:</div> <div class="quote_body"> <p>nope.... cos u intergrate 1/V dV you will get ln v_f&nbsp;- ln v_i&nbsp;= ln(v_f/v_i).</p> </div> </blockquote> <p><br /> Yeah as i state, i dunno the formula. TS's formula is wrong in #1 post.</p> <blockquote> <p>Chapter 19, P13, i think you need to find the volume using the P1V1 = P2V2... then use the <span style="color: #ff0000;">W = nRT ln (Vf - Vi)</span><br /> which is also W = PV lv (Vf - Vi)</p> <p>&nbsp;</p> </blockquote> Thu, 10 Apr 2008 19:27:55 +0800 zh.sgforums.com:2297:313906:8002500 weewee http://zh.sgforums.com/forums/2297/topics/313906