er 4Practice Exercise4.1mol Al = 3.47 g Al1 mol Al26.98 g Al    = 0.129 mol Al4.2Uncertainty in MOLES = ±0.002 g24241 mol KSO174.25 g KSO    = ±1.15 x 10-5 mol K2SO44.3 Find the MASS of 5.64 × 1018 molecules of C18H38 (MW = 254.50 g/molg = 5.64 × 10181838183823183818381 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 × 1018 molecules of C18H38.4.4 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 sucrose236.02210 molecules sucrose1 mol sucrose ×    =±3.5× 1018 molecules of sucrose4.5 Aluminum sulfate: Al2(SO4)3, the aluminum is Al3+mole Al3+ = 0.0774 mol SO42–3+242 mol Al3 mol SO −    = 0.0516 mol Al3+ 4.6 The formula of dinitrogen pentoxide is N2O5 ( )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      