Calculate the molar mass of NaCI (sodium chloride) C_6H_12O_6 (glucose) C_2H_6O

Question

Calculate the molar mass of NaCI (sodium chloride) C_6H_12O_6 (glucose) C_2H_6O (ethanol) HCI (hydrochloric acid) C_16H_18N_2O4S (penicillin G) C_19H_2O_2 (testosterone) Classify as True or False. Explain if False As a mole always has the same number of particles, one mole of two different substances have the same volume. A mole of sulfur has less mass than a mole of lithium A mole of potassium dichromate (K_2Cr_2O_7) has a mass of 394.2 g A mole of sucrose (C_12H_22O_11) has a mass of 342.3 g Questions and problems. Equations for chemical reactions, page 227. Answer the 7.28, 7.30, and 7.3 Questions and problems. Types of reactions, page 232. Answer 7.34, 7.36, and 7.38 Balance the following equations: CO + O_2 rightarrow CO_2 C_5H_10O_2 + O_2 rightarrow CO_2 + H_2O Al + O_2 rightarrow Al_2O_3 Al_2(SO_4)_3 + Ca(OH)_2 rightarrow Al (OH)_3 + Ca (SO_4) Cr + O_2 rightarrow Cr_2O_3 Hg (OH)_2 + H_3PO_4 rightarrow Hg_3 (PO_4)_2 + H_2O Let's suppose that in reaction d), question above, the initial amount of Ca(OH)_2 is 370g and enough AI_2(SO_4)_3 is available. How much AI(OH)_3 is produced?

Explanation / Answer

For calculating the molar mass, one shoud know the atomic weights.

For Nacl, atomic weights : Na= 23 and Cl =35.5

Since NaCl contains 1 atom of sodiu 1 atom of Chlorine, moalr mass of NaCl= 23+35.5 =58.5g/mole

Atomic weights : C=12, H=1 and O=16

Molecular weights of C6H12O6= 6*12+12*1+6*16= 180

Molecular weight of C2H6O= 2*12+6*1+16= 46

Molecular weight of HCl= 1+35.5= 36.5

Atomic weight of N=14, S=32, Molar mass of C16H18N2O4S=16*12+18*1+14*2+16*4+32=334 g/mole

Molar mass of testosterone (C19H28O2)= 19*12+28*1+2*16= 288

8. a) 1 mole of any gas at STP ( standard conditions of temperature and pressure) ocupies same volume. Unles the substances are gases , they do not occupy same volume. Hence it is false.

1 mole of sulfur = 32 gm, 1mole of lithium= 7 gm, 1 mole of sulfur has more mass than leithium and hence false.

Atomic weights : K=39, Cr=52 and O=16

Mole = mass/molecular weight

For 1 mole, mass= molecular weight

Molar mass of K2Cr2O7= 2*39+ 2*52+7*16=294. So 394.2 gm is incorect.

Molar mass of 1 mole of C12H22O11= 12*12+22*1+16*11=342. Hence correct.

CO+1/2O2-----àCO2

C5H12O2 +6.5 O2----à 5CO2 + 5H2O

2Al+ 3/2O2----à Al2O3, Al2(SO4)3 + 3Ca(OH)2-----à2Al(OH)3 + 3CaSO4, 2Cr +3O2-à 2Cr2O3.

3Hg(OH)2 +2H3PO4------àHg3(PO4)2 +6 H2O

The balanced equation is

Al2(SO4)3 + 3Ca(OH)2-----à2Al(OH)3 + 3CaSO4

Moles of Ca(OH)2 in 370 gm= mass/Molecular weight = 370/74=5

This is limitijng reactants, 3 moles of Ca(OH)2 gives 2 mole of Al(OH)3

5 moles of Ca(OH)2 gives 5*2/3= 3.33 moles of Al(OH)3

Molar masss of Al(OH)3= 78, mass of Al(OH)3= 3.33*78=259.74 gms

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