Can someone help me with my stoichiometry problems in Chemistry?

Question

I put all my questions into an image file. Thanks to whoever helps me! I tried all of these questions, but I am getting the wrong answers. Please help me

http://img171.imageshack.us/img171/1742/chemistryhelplh5.jpg

coza b, thanks for helping me on those. You are truly awesome for doing that. I think I understand how to do them now!

Answer 1

8.
All water evaporated = water loss = 11.88 - 7.6 = 4.28 g.
moles of water = 4.28/18 = 0.2378 moles

13.
Molecular weight
CaF2=78
HF=20

source: http://www.uwosh.edu/faculty_staff/kedrowsk/yield_calc.htm
percent yield = actual yield/theoretical yield


theoretical yield = 2x(9/78)moles = 0.2308 (based on coefficients, 1 mole of CaF2 produce 2 moles of HF)
actual yield = (1.76/20)moles = 0.088
percent yield = 0.088/0.2308 = 38.12%

16.
Atomic weight of Fe = 56
mol weight of Fe2O3 = 160
4Fe + 3O2 --> 2Fe2O3
Fe stays as Fe = 7/8x627 = 548.625
Fe become Fe2O3 = 1/8x627 = 78.375 ==> 78.375/56 = 1.4 moles,
Fe2O3 = 2/4 x 1.4 moles x 160 = 112 g
total wt = 112+548.625= 660.625 g

17.
assume all glucose become energy+water+Co2
(mol wt=180)
C6H12O6 + 6O2 --> 6CO2 + 6H2O
300 g/day

total CO2 = 6 x (300/180) moles/day x 365 days/year x 6 billion x 44 g/mole CO2
= 9.636 x 10^14 g/year

23.
Mr Fe2O3 = 160 g/mole
1000 kg Fe = 1000/56 kmoles
Fe2O3 needed = 1/2 x 1000/56 = 1000/112 kmoles
Fe2O3 needed = 1000/112 x 160 = 1428.57 kg
purity = 1428.57/2250 = 63.492%

Answer 2

first of all, enable's get rid of the beaker from the uncooked records - subtract its mass, 50.fifty two g from all records. a million.) beginning up good cloth = fifty two.40 3 - 50.fifty two = a million.ninety one g 2.) mass of product (NaCl) = fifty two.sixty 3 - 50.fifty two = 2.11. So we are beginning with a million.ninety one-g of an unknown substance and discover that we get produced 2.11 grams of NaCl. we are charged with looking the identity of the unknown. Now for the priority: we could desire to apply each and every equation to calculate the theoretical yield of NaCl and then evaluate it to the extremely yield. a.) Sodium carbonate- a million.ninety one g Na2CO3 x ( a million mol Na2CO3 / 106-g Na2CO3) x (2 mol NaCL / a million mol Na2CO3) x (fifty 8.5-g NaCl / a million mol NaCl) = 2.11 - g NaCl nicely, we are fortunate...have been given IT ON FIRST try. The unknown replace into sodium carbonate, yet we could be effective by skill of doing the different additionally. b.) a million.ninety one g NaHCO3 x (a million mol NaHCO3 / 80 4-g NaHCO3) x (a million mol NaCl / a million mol NaHCO3) x (fifty 8.5-g NaCl/1mol NaCl) = a million.33-g NaCl

Answer 3

I need some help with that stuff as well. I can do some stoichiometry, and from my understanding it's basically converting the grams you want to moles, then multiplying that by the ratio, then multiplying it back to grams.

Answer 4

sorry, you should go talk to your teacher BEFORE school not before or after class or during either you lose brownie points for that you gain for before school

Answer 5

i would like to help you but i cant see the questions