Molecular  Calculator Tutorial

2.1 Calculate moles:

a) 12 grams of NaCl

b) 23 grams of CaO

c) 9.43 grams of CuSO4*5H2O

Solutions:

a) 12gNaCl

b) 23gCaO

c) 9.43gCuSO4*5H2O

2.2 Calculate grams:

a) 0.1 moles of CuCl2

b) 0.5 moles of NH4Cl

c) 2 moles of CaSO4*5H2O

Solutions:

a)1mCuCl2

b) 0.5mNH4Cl

c) 2mCaSO4*5H2O

2.3 Calculate moles of carbon (C) in:

a) 3.2 moles of CH4

b) 0.5 moles of HCN

c) 2.17 moles of K4Fe(CN)6

Solutions:

a) 3.2mCH4

b) 0.5mHCN

c) 2.17mK4Fe(CN)6

2.4 Calculate grams of oxygen (O) in:

a) 3 grams of CaO

b) 21 grams of H2O2

c) 0.23 grams of BaSO4

Solutions:

a) 3gCaO

b) 21gH2O2

c) 0.23gBaSO4

2.5 Calculate moles of hydrogen (H) in:

a) 1.4 grams of LiH

b) 0.3 grams of H2O

c) 12 grams of CH3CH2OH

Solutions:

a) 1.4gLiH

b) 0.3gH2O

c) 12gCH3CH2OH

2.6 Calculate grams of Sodium (Na) in:

a) 0.6 moles of NaCl

b) 3.4 moles of Na2CO3

c) 2.3 moles of NaH2PO4

Solutions:

a) 0.6mNaCl

b) 3.4mNa2CO3

c) 2.3mNaH2PO4

2.7 Calculate % Calcium (Ca) in:

a) 2.1 moles of CaO

b) 0.6 moles of CaCl2

c) 3.2 moles of Ca3(PO4)2

Solutions:

a) 2.1mCaO

b) 0.6mCaCl2

c) 3.2mCa3(PO4)2

2.8 Calculate % Fluorine (F) in:

a) 1.2 grams of HF

b) 2.7 grams of MgF2

c) 0.9 grams of AlF3

Solutions:

a) 1.2gHF

b) 2.7gMgF2

c) 0.9gAlF3

2.9 Calculate:

a) % K, Cr and O in K2CrO4.

b) Grams of: Ca, C and O in 0.3 mol CaCO3.

c) Moles of Pb and O in 12grams PbO2.

Solutions:

a) K2CrO4.

b) 0.3mCaCO3.

c) 12gPbO2.

2.10 Calculate grams and moles (all elements) in Mg3(PO4)2.

Solution:

Mg3(PO4)2

2.11 Calculate moles:

a) 2 moles of Na in NaCl

b) 0.3 moles of Cl in AlCl3

c) 3.6 moles of P in Ca3(PO4)2

Solutions:

a) 2mNa,NaCl

b) 0.3mCl,AlCl3

c) 3.6mP,Ca3(PO4)2

2.12 Calculate grams of:

a) CaO containing 2 grams of O

b) HCl containing 5 grams of Cl

c) Fe2O3 containing 2.4 grams of Fe

Solution:

a) 2gO,CaO

b) 5gCl,HCl

c) 2.4gFe,Fe2O3

2.13 Calculate moles of Potassium (K) in:

a) KNO3 containing 3.2 moles of O

b) KClO4 containing 0.2 moles of Cl

c) CaCl2 containing 1.4 moles of Ca

Solutions:

a) 3.2mO,KNO3

b) 0.2mCl,KClO4

c) 1.4mCa,CaCl2

2.14 Calculate grams of Nitrogen(N) in:

a) NO containing 12 grams of O

b) NH3 containing 0.5 grams of H

c) NH4Cl containing 3.0 grams of Cl

Solutions:

a) 12gO,NO

b) 0.5gH,NH3

c) 3.0gCl,NH4Cl

2.15 Calculate moles of barium (Ba) in:

a) BaO containing 5.4 grams of O

b) BaCl2 containing 3.7 grams of Cl

c) BaCO3 containing 1.0 grams of C

Solutions:

a) 5.4gO,BaO

b) 3.7gCl,BaCl2

c) 1.0gC,BaCO3 2.16 Calculate grams of Cu in:

2.16 Calculate grams of Cu in:

a) CuS containing 0.6 moles of S

b) CuCl2 containing 6.4 moles of Cl

c) CuSO4*5H2O containing 7.8 moles of O

Solutions:

a) 0.6mS,CuS

b) 6.4mCl,CuCl2

c) 7.8mO,CuSO4*5H2O

2.17 Calculate % bromide (Br) in:

a) NaBr containing 2.1 moles of Na

b) CaBr2 containing 3.0 moles of Ca

c) AlBr3 containing 0.2 moles of Al

Solutions:

a) 2.1mNa,NaBr

b) 3.0mCa,CaBr2

c) 0.2mAl,AlBr3

2.18 Calculate % lithium (Li):

a) LiI containing 9.0 grams of I

b) Li2O containing 2.8 grams of O

c) LiHCO3 containing 1.0 grams of C

Solutions:

a) 9.0gI,LiI

b) 2.8gO,Li2O

c) 1.0gC,LiHCO3

2.19 Calculate

a)% Na, C and O if Na2CO3 contains 4 grams of O.

b)Grams of iron and oxygen in Fe2O3 containing 0.8 moles of Fe.

c)Moles of lead, carbon and hydrogen in Pb(C2H5)4 containing 4.0 grams of hydrogen.

Solutions:

a) 4gO,Na2CO3

b) 0.8mFe,Fe2O3

c) 4gH,Pb(C2H5)4

2.20 Calculate %, grams and moles of all elements in C4H9OH.

Solution:

C4H9OH

2.21 Calculate max.amount of formed Ca3(PO4)2 using 3 grams of Ca ,10 grams of O and 14 grams of P?

Solution:

Determine by calculating following argumented formulas: 3gCa,Ca3(PO4)2 and 10gO,Ca3(PO4)2 and 14gP,Ca3(PO4)2

2.22 How many moles of Be must be used to make 245 grams BeCl2?

Solution:

245gBeCl2

2.23 The CuSO4*5H2O -compound release water when heated. How much mass will evaporate in this process?

Solution:

mass of (CuSO4*5H2O) - mass of (CuSO4) = mass of 5H2O

2.24 Determine empirical formula:

a) 92.83% lead and 7.67% oxygen.

b) 31.9% potassium, 28.9% chlorine and 39.2% oxygen.

Solution: Vary element composition of formula and investigate the element ratio. It will simplify calculation if one of the elements in the trial formulas are argumented by grams.

a) First argumented trial formula , 92.83gPb,PbO shows a plausible element mass ratio.

b) First argumented trial formula, 31.9gK,KClO indicates to little oxygen. Second argumented trial formula 31.9gK,KClO2 also indicates to little oxygen. Third argumented formula 31.9gK,KClO3 shows a correct element ratio.

2.25 0.3 grams of metallic silver was dissolved. A precipitate (0.399 grams of AgX) formed after adding a unknown substance. Determine X knowing that X=Cl- or X=Br-.

Solution: Determine by the use of argumented trial formulas (0.3g) and compare results: 1) 0.3gAg,AgBr or 2) 0.3gAg,AgCl .

2.26 A solution of dissolved Ca(OH)2 was added CO2. A white precipitate formed. The precipitate was filtered, dried and weighed. (2.35 grams). How many grams of Ca was involved in the precipitation process?

Solution:

Ca(OH)2+CO2>CaCO3+H2O

2.35gCaCO3

2.27 2 grams of Al was added HCl:

2Al(s) + 6HCl(aq)=2AlCl3 + 3H2

a) How many grams of AlCl3 was formed in the reaction?

b) How many moles of HCl was used forming AlCl3?

Solutions:

a) 2gAl,AlCl3

b) moles of AgCl3*3= moles of HCl

2.28 3 grams of Fe reacts with 1.29 grams of O2 forming a pure iron compound.

a) Decide the empiric formula?

Solution:a)First argumented trial formula, 3gFe,FeO contains to small amount of oxygen. Second argumented trial formula, 3gFe,FeO2 contains to much oxygen. Third argumented trial formula, 3gFe,Fe2O2 contains to small amount of oxygen. At least, the formula 3gFe,Fe2O3 shows a correct iron/oxygen ratio.