How do I find how many moles of hydrogen atoms...?

1: How many moles of hydrogen atoms are there in:


a) 1.60 moles of zinc hydroxide


b) 0.20 moles of sodium hydrogenphosphate-12-water





Also, how do I find the mass of the following samples?


a) 2.65 moles of phosphoric acid, H3PO4





b) 0.0080 moles of mercury (II) iodide





c) 1.60 moles of yellow phosphorous, P4





Please help me. Thankyou.


c) 0.350 moles of ammonium hydrogensulfate





Note: How do I do this...please explain it all to me and show working so that I know how to do these. Do I need to know the formula for these 1st question ones? Please help me.

How do I find how many moles of hydrogen atoms...?
moles=grams/atomic mass





atomic mass of H is about 1 so one gram equals one mole. Thats only for H though
Reply:You MUST know the formulas to answer Q1.


a. The compound is Zn(OH)2.


Since hydrogen appears as H2, 1 mole of hydrogen supplies 2 g-atoms. In this case, you HAVE 2 g-atoms in the hydroxide, so there is one mole of H2 per 1 mole of the compound. Ans=1.6


b. The compound is Na H2PO4 (phosphoric acid has 3 ionizable hydrogens, and thus with a anion like sodium can form 3 different compounds.


Here you again have 2-atoms of the hydroxide


per mole of the compound. So Ans= 0.20


c. The compound is NH4 HSO4 . Each mole of this contains 5 g-atoms of H. So the moles in each mole is 2.5. Ans= 0.875 moles.





For your masses, you need mole weights and to know the atomic numbers of the component elements


For H3PO4, mass = 3(mass H)+ 1(mass P) + 4(mass O). The masses are 1, 35 and 16 respectively, so the answer would be 102g/mole


So multiply this by 2.65 to get mass.





The compound is HgI2.


The mass is (if I have my numbers right) is


198+2(127)= 452


Multiply by 0.008 to get mass





For P4 mass= 4P or 140. Mult by 1.6 to get answer.
Reply:1. a) 1.60 mol Zn(OH)2, 1 mol Zn(OH)2 = 2 mol H


1.60 mol Zn(OH)2 x (2mol H/1mol Zn(OH)2 )


= 3.20 mol H


b) NaH2PO4.12H2O


0.20 mol NaH2PO4.12H2O x (26 mole H/ 1mol NaH2PO4.12H2O) =5.2 mol H





2. a) 2.60 mol H3PO4 x (98.0 g/mol)=254.8=255 g


b) 0.0080 mol HgI2 x (454.4g/mol) =3.6 g


c) 1.60 mol P4 x(124g/mol)=198g


3. 0.350 mol NH4HSO4 x (115g/mol)=40.3 g
Reply:the first answer is 1.6;





[1.6 moles Zn(OH)2] TIMES [2 mol OH/1 mol Zn(OH)2] TIMES [1 mol H/2 mol OH] = 1.6 mol H2





the equations i used for that: Zn + (OH)2 --%26gt; Zn(OH)2





and: H2 + 2O --%26gt; (OH)2





remember: hydrogen is diatomic. when isolated, it only comes as H2. that is the reason why the answer can't be 3.2 grams H