3) What is the % by mass of oxygen in H 2 SO 4 ? [ GFM=98]. % COMP (MASS) = PART X 100 WHOLE. % Oxygen = 63.9976 X 100 98. = 65.3 % ~ 65 %.
3) What is the % by mass of oxygen in H2SO4? [ GFM=98]
% COMP (MASS) = PART X 100
% Oxygen = 63.9976 X 100
= 65.3 % ~ 65 %
#5) A hydrate is a compound that includes water molecules within its crystal structure. During an experiment to determine the percent by mass of water in a hydrated crystal, a student found the mass of the hydrated crystal to be 4.10 grams. After heating to constant mass, the mass was 3.70 grams. What is the percent by mass of water in this crystal?
% H2O =
4.10 g – 3.70 g
9.8 % water
% H2O =
This is a modified version of part/whole x 100 from the reference tables!
7) Given the reaction:
6 CO2 + 6 H2O 1C6H12O6 + 6 O2
a) What is the total number of moles of waterneeded to make 2.5 moles of C6H12O6?
X = 15 moles of water
Theoretical mole ratio
#13) A compound contains 0.5 moles of sodium, 0.5 moles of nitrogen, and 1.0 moles of hydrogen. The empirical formula of the compound is
Multiply subscripts by 2
Subscripts can not be decimals, to get rid of a 0.5 decimal multiply all subscripts by 2!
The new subscripts are:
#15) A compound contains 40% CALCIUM, 12% CARBON and 48% OXYGEN by mass. What is the empirical formula of this compound?
Assume 100g of the sample, this will allow you to assume 40% is 40 grams. Total mass does NOT affect % composition.