what number do you add to get the H2 ,O3 ,CO ,NH3 ,N2O4 ,C4H10 formula mass ?
Answers
35
Chapter 4Practice Exercise
4.1
mol Al = 3.47 g Al1 mol Al26.98 g Al
= 0.129 mol Al
4.2
Uncertainty in moles = ±0.002 g
2424
1 mol KSO174.25 g KSO
= ±1.15 x 10
-5
mol K
2
SO
4
4.3 Find the mass of 5.64 × 10
18
molecules of C
18
H
38
(MW = 254.50 g/molg = 5.64 × 10
18
183818382318381838
1 mol CH254.50 g CH1 mol CH6.02210 molecules CH
×
= 2.38 × 10
–3
gg = 2.38 × 10
–3
g = 0.00238 gMany laboratory balances can measure 1 mg (0.001 g); therefore, it is possible to weigh 5.64 × 10
18
molecules of C
18
H
38
.4.4 Formula mass of sucrose = (12 C)(12.011 g/mol) + (22 H)(1.0079 g/mol) +(11 O)(15.9994 g/mol) = 342.299 g/molIf the massing uncertainty is ±0.002 g what is the uncertainty of mol of sucrose?Uncertainty of mol of sucrose = ±0.002 g1 mol sucrose342.299 g
= ±5.8 × 10
–6
mol sucroseUncertainty of molecules of sucrose = ±5.8 × 10
–6
mol sucrose
23
6.02210 molecules sucrose1 mol sucrose
×
=±3.5× 10
18
molecules of sucrose4.5 Aluminum sulfate: Al
2
(SO
4
)
3
, the aluminum is Al
3+
mole Al
3+
= 0.0774 mol SO
42–
3+24
2 mol Al3 mol SO
−
= 0.0516 mol Al
3+
4.6 The formula of dinitrogen pentoxide is N
2
O
5
( )
2 mol Nmol N = 8.60 mol O5 mol O
= 3.44 mol N atoms4.7
( )
1 mol O2 mol Fe55.85 g Feg Fe = 25.6 g O = 59.6 g Fe16.00 g O3 mol O1 mol Fe