// Acids & Bases - pH of Solutions of Weak Acids Script thepage="pH of Solutions of Weak Acids" //updated 11/18/02-netscape 7 //global variables //refnumber=114 theanswer="" attempts=0 phans=0 corrt=0 totl=0 which=0 function parts(p1,p2,p3,p4,p5){ this.p1=p1 this.p2=p2 this.p3=p3 this.p4=p4 this.p5=p5 } function data(formula,name,K){ this.formula=formula this.name=name this.K=K } checkstring="z0123456789" hsym="[H+]" avalue="(Ci × Ka)1/2 = "+hsym acids=new Array() acids[0]=new data("CH3COOH","Acetic",1.8e-5) acids[1]=new data("C6H5COOH","Benzoic",6.5e-5) acids[2]=new data("HClO","Hypochlorous",3.5e-8) acids[3]=new data("CH2ClCOOH","Chloroacetic",1.4e-3) acids[4]=new data("HCOOH","Formic",1.8e-4) acids[5]=new data("HF","Hydrofluoric",3.5e-4) acids[6]=new data("HNO2","Nitrous",4.5e-4) acids[7]=new data("HClO2","Chlorous",1e-2) acids[8]=new data("CH3CH(OH)COOH","Lactic",1.4e-4) acids[9]=new data("HCN","Hydrocyanic",4.9e-10) acids[10]=new data("HO2C2OOH","Oxalic",5.4e-2) acids[11]=new data("H2SO3","Sulfurous",1.3e-2) acids[12]=new data("H3PO4","Phosphoric",7.1e-3) acids[13]=new data("H2CO3","Carbonic",4.9e-7) acids[14]=new data("H2S","Hydrosulfuric",1.1e-7) acids[15]=new data("H3BO3","Boric",5.8e-10) function constants(){ var cont=window.open("","cont","scrollbars=yes,width=300,height=300") cont.document.writeln (""); cont.document.writeln ("Ionization Constants"); cont.document.writeln (""); cont.document.writeln ("Acids"); for(k=0;k<=15;k++){ theK=acids[k].K theK=number(theK,2,2) cont.document.writeln("")}; cont.document.writeln("
",acids[k]['name'],""); cont.document.writeln("",showformula(k),""); cont.document.writeln("",theK,"
"); cont.document.writeln(""); cont.document.close(); cont.focus(); } ansphrase=new Array() compare=new Array() compare[0]=new Array(" less "," valid") compare[1]=new Array(" greater "," invalid ") ansphrase[1]=new parts(" acid has a Ka of ",". First, calculate the value for the weak acid approximation.
"," Since this is "," than 5% of the inital concentration ",", the approximate value is ",".") insphrase=new Array(" and the answer is pH = "," and you must calculate the 'exact' answer using either successive approximations or the quadratic. This yields [H+] = ") pathway=new Array() pathway[0]=new Array(" less than "," valid ") pathway[1]=new Array(" greater than "," invalid ") function startit(){ clear() totl++ document.forms[0].results.value=document.forms[0].theans.value="" document.forms[0].total.value=totl which=Math.floor(acids.length*Math.random()) getconc() } function getconc(){ first=0 while(first<11)first=Math.ceil(100*Math.random()); conc="0."+zero()+first getanswer(which,conc) buildquest(which,conc) } function zero(){ added="" for(j=1;j<=Math.floor(3*Math.random());j++)added+="0"; return added } function getanswer(which,conc){ approx=Math.sqrt(conc*acids[which].K) check=.05*conc approx=number(approx,3,3) check=number(check,3,3) if(approx>check && Math.random()<.75){getconc()} else{ if(approx("+conc+" × "+number(acids[which].K,3,2)+")1/2 = "+number(approx,3,2) theanswer+=("
"+ansphrase[1].p3+compare[vkey][0]+ansphrase[1].p4+"("+number(check,3,2)+")"+ansphrase[1].p5+compare[vkey][1]+insphrase[vkey]) if(vkey==0)theanswer+=phans; else theanswer=theanswer+number(exans,3,3)+" and pH = "+phans; } function buildquest(){ thequest="What is the pH of a "+conc+"M solution of " Math.random()>.5?thequest+=(acids[which].name+" acid?"):thequest+=(getformula()+"?"); showquest(thequest) } function answer(ans){ if(tried==1)alert("You've done this one. Get a new problem.") else{ if(tried==2){totl++;document.forms[0].total.value=totl} attempts++ if(ans>.95*phans & ans<1.05*phans){ document.forms[0].results.value="Correct" corrt++ document.forms[0].correct.value=corrt tried=1 } else{ document.forms[0].results.value="Incorrect" tried=2 }} } function showformula(k){ theformula="" teststring=acids[k].formula for(j=0;j0?theformula+=""+teststring.charAt(j)+"":theformula+=teststring.charAt(j); } return theformula } function getformula(){ theformula="" teststring=acids[which].formula for(j=0;j0?theformula+=""+teststring.charAt(j)+"":theformula+=teststring.charAt(j); } return theformula }