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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: nordqvist on September 28, 2011, 06:46:50 PM

Title: Stoichiometry Question
Post by: nordqvist on September 28, 2011, 06:46:50 PM

Hi there guys, I've tried balancing this equation but it seems to be too hard. Is my approach to the question the right one. How would you solve it?

A mass of 21.5 grams of calcium hydroxide reacts with an excess of phosphoric acid. What mass of calcium phosphate could be recovered from solution?

   a.    31.6 grams
   b.  326 grams
   c.   284 grams
   d.   186 grams
   e.  94.7 grams

Title: Re: Stoichiometry Question
Post by: Arkcon on September 28, 2011, 08:59:46 PM

OK.  Let's start by writing the reactants and known products using chemical notation.  There are subscript buttons above for you to use.  Lets see if you can balance the equation

Title: Re: Stoichiometry Question
Post by: nordqvist on September 28, 2011, 09:40:06 PM

2H₃PO₄+3Ca(OH)₂ -> Ca₃(PO₄)₂ + 6H₂O

Title: Re: Stoichiometry Question
Post by: Hunter2 on September 29, 2011, 01:13:30 AM

Now calculate how many mole is 21,5 g Calciumhydroxide.  How many mole of the phosphate correspond to it. Calculate back the mass of the Phosphate.