Page 248 - Chemistry eBook

Percent Composition Problems
How to Solve Percent Composition Problems:
Percent Error % error = measured value – accepted value × 100 accepted value
Table T
Important Formulas and Equations
Density
Mole Calculations
m d = V
number of moles =
d = density m = mass
V = volume
given mass gram-formula mass
Reffy, Table T (p.12)
1. Find the mass of the part. Make sure to find the entire part.
Percent Composition
% composition by mass =
mass of part
× 100
mass of whole
What’s the percent composition of H in H O? Find the mass of H .
Concentration
2
2
2. Find the mass of the entire molecule.
3. Plug the values into the equation and solve.
4. Multiply your answer byC1o0m0bintoedgGeatstLhaewpercentag=e. T1 T2
parts per million = mass of solute mass of solution
× 1000000
I hope I get 100% on my Chemistry Regents!”
= molarity of OH–
molarity = P1V1 P2V2
P = pressure
V = volume
T = temperature
M = molarity of H+ AB
moles of solute liter of solution
What is the percent composition of H in H2O?
1. H’satomicmasTsitriasti1o.nH:1x2=2M V =M V
M
2. 3.
2 18
VA = volume of acid VB = volume of base q = mC∆T q = heat Hf = heat of fusion
2AABB
H2O’s atomic mass: H’s mass is 2 (1 x 2 = 2); O’s mass is 16; 2 + 16 = 18
× 100
Heat
Temperature
4. 0.11111 × 100 = 11.1%
q = mHf m = mass Hv = heat of vaporization q T=hmeHpercent compCos=itspioecnifiocfhHeat cinapaHcitOy is 11.1%
v22 ∆T = change in temperature
K = °C + 273 K = kelvin
°C = degree Celsius
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