thepage="Gen Stoichiometry(133)"
//11'20/02-updated netscape 7
refnumber=173
attempts=0
totl=0
corrt=0
first=0
second=0
theanswr=0
therows=""
theanswer=""
qphrase=new Array()
seq=new Array()
theunits=new Array("moles","grams")
introphrase="For the balanced equation shown below, how many "
insert=new Array(" will react with "," will be produced by "," reacted, if "," will be produced, if ")
finish=new Array("?","?"," are produced?"," are produced?")
ansphrase=new Array("To answer this question, you use the following ratio from the balanced equation:<br><br>","<br>Setting the ratio from the balanced equation equal to the ratio described in the problem yields<br>","<br>Rearranging the equation and solving for "," yields:<br> ")
//clears values and selects an equation using the choose function(part of reactionsets.js)
function startit(){
	clear()
	totl++
	document.forms[0].total.value=totl
	document.forms[0].results.value=""
	choose()
	buildarray()
	buildquestion()
}
//thefollowing builds an array of the formulas, stoichiometric coeffs and masses in balanced equation
//each array row consists of the formula, the coeff and the reaction mass
//there is one row per compound
function buildarray(){
	therows=new Array()
	for(j=0;j<coeffs[choice].length;j++){
		therows[j]=new Array()
		therows[j][0]=getformula(j+2)
		therows[j][1]=coeffs[choice][j]
		therows[j][2]=getmass(j+2)
	}
	//showquest(therows)
}

//choice is the index of the selected reaction
function buildquestion(){
	first=Math.floor(coeffs[choice].length*Math.random())
	second=first
	while(second==first)second=Math.floor(coeffs[choice].length*Math.random())
	//determines if they're both reagents, both products or one of each.
	if(first<=splt)second<=splt?option=0:option=1;
	else second<=splt?option=2:option=3;
	//this creates a random factor that will generate the values for the question
	factor=0
	while(factor<.05)factor=Math.random();
	if(Math.random()>.5)factor=1/factor
	factor=number(factor,3,3)
	thedata=new Array()
	thedata[0]=factor*therows[first][1]
	thedata[2]=factor*therows[second][1]
	thedata[1]=factor*therows[first][2]
	thedata[3]=factor*therows[second][2]
	for(var j=0;j<4;j++)thedata[j]=number(thedata[j],3,3)
	Math.random()>.5?findex=0:findex=1;
	Math.random()>.5?sindex=0:sindex=1;
	sindex==0?theanswr=thedata[2]:theanswr=thedata[3];
	thequest=introphrase+theunits[sindex]+" of "+therows[second][0]+insert[option]+thedata[findex]+theunits[findex]+ " of "+therows[first][0]+finish[option]+"<br>"+equation+"<br>"
	buildanswer(first,second,findex,sindex)
	showquest(thequest)
}
function buildanswer(first,second,findex,sindex){
	eqn1="("+theunits[sindex]+" of "+therows[second][0]+")/("+theunits[findex]+" of "+therows[first][0]+")<br>"
	eqn2=therows[second][sindex+1]+"/"+therows[first][findex+1]+"=(<b>"+theunits[sindex]+" of "+therows[second][0]+"</b>)/"+thedata[findex]+"<br>"
	eqn3=therows[second][sindex+1]+"/"+therows[first][findex+1]+"*"+thedata[findex]+"="+thedata[sindex+2]
	theanswer=ansphrase[0]+eqn1+ansphrase[1]+"<br>"+eqn2+"<br>"+ansphrase[2]+"<b>"+theunits[sindex]+" of "+therows[second][0]+"</b><br>"+eqn3
}	

function answer(ans){
	if(tried==1)alert("You've done this one. Get a new problem!")
	else{
	attempts++
	if(tried==2){totl++;document.forms[0].total.value=totl}
	if(ans>.95*theanswr & ans<1.05*theanswr){
		document.forms[0].results.value="Correct"
		corrt++
		document.forms[0].correct.value=corrt
		tried=1
	}
	else{
		document.forms[0].results.value="Incorrect"
		tried=2
	}}
}