1) A solution containing a linear molecule is dripped onto a dish of water. the molecules has one polar end and one non polar end. which end will end up embedded in the surface of the water,? and why?

2) C₇H₆O₃ + C₄H₆O₃ = C₉H₈O₄ + CH₃COOH, How many grams of acetic anhydride are needed to react with 4.5 of salicylic acid?

3) C₄H₈+CH₄O=C₅H₁₂O, 26.3 g of isobutylene is reacted with excess methanol and 32.8g of MTBE is formed. what is the percent error for this reaction?

4) K₂PtCl₄ + 2 NH₃ = Pt(NH₃)₂Cl₂ +2 KCl, assume that 10 g of K₂PtCl₄ and 10 g of NH₃ are allowed to react, what is the final mass of cisplatin that will be formed?

 

1.

A water molecule (H₂O) is formed by a combination of two hydrogen atoms and one oxygen atom. Oxygen is more electronegative than hydrogen. The oxygen atom of the water molecule carries a partial negative charge and the hydrogen atom carries a partial positive charge, thus water is polar. Water has hydrogen bonding. The linear molecule has one polar end and one nonpolar end.  The polar end of the linear molecule is embedded in the surface of the water. We know, a polar molecule attracts other polar molecules. Water is a polar molecule so it attracts the polar end of the linear molecule.

2.

The chemical equation for the reaction is:

 C₇H₆O₃ + C₄H₆O₃ ---> C₉H₈O₄ +CH₃CO₂H

The molar mass of Salicylic acid C₇H₆O₃ = 138.121 g/mol

Calculate the moles of Salicylic acid:

The number of mole of salicylic acid =  4.5 g*1mol/138.121 g = 0.03258 moles

Calculate the moles of acetic anhydride needed to react with 4.5 of salicylic acid:

According to the balanced chemical equation, 1 mol of C₇H₆O₃ reacts with 1 mol of C₄H₆O₃

Therefore,  0.03258 moles of C₇H₆O₃ will react with =0.03258 mol C₇H₆O₃ *1 mol of C₄H₆O₃/1 mol C₇H₆O₃ = 0.03258 mol of C₄H₆O₃

Calculate the grams of acetic anhydride needed to react with 4.5 of salicylic acid:

The molar mass of C₄H₆O₃ = 102.09 g/mol

The mass of C₄H₆O₃ = 0.03258 mol *102.09 g/mol =3.3 g

3.

The balanced chemical equation for the reaction is:

C₄H₈+CH₄O---->C₅H₁₂O

Calculate the moles of isobutylene:

The molar mass of  C₄H₈ =56.11 g/mol

The number of mole of C₄H₈ = 26.3 g*1mol/56.11 g =0.468722 moles

Methanol is an excess reactant. Therefore, isobutylene will be a limiting reactant, and the mass of MTBE is formed depends on it.

The mass of MTBE is formed =0.468722 moles C₄H₈* 1molC₅H₁₂O/1molC₄H₈ * 88.15 g C₅H₁₂O/1mol C₅H₁₂O =41.3g C₅H₁₂O

The percent error = [theoretical value - experimental value ] / theoretical value x 100

Percent error = [(41.3g -32.8g )/ 41.3g]*100

Percent error = 20.6%

4.

The balanced chemical equation for the reaction is:

K₂PtCl₄ + 2 NH₃ = Pt(NH₃)₂Cl₂ +2 KCl,

Molar mass of K₂PtCl₄ = 415.09 g/mol

The number of mole of K₂PtCl₄ = 10 g*1mol/ 415.09 g = 0.0241 moles

Molar mass of NH₃= 17.031 g/mol

The number of mole of NH₃ = 10 g*1mol/17.031 g0.587 moles

According to the balanced chemical equation, 1 mol of K₂PtCl₄ reacts with 2mol NH₃ 

Therefore, 0.0241 moles of K₂PtCl₄ will react with =0.0241 mol K₂PtCl₄ *2 mol NH₃ of /1 mol K₂PtCl₄ = 0.0482mol of NH₃ 

But in reaction, there is more moles of NH₃ , so NH₃  is an excess reactant.

K₂PtCl₄ is a limiting reactant and mass of cisplatin produced depends on it.

The final mass of cisplatin that will be formed =0.0241 moles K₂PtCl₄ *(1mol Pt(NH₃)₂Cl₂ / K₂PtCl₄ )*( 301.1 g Pt(NH₃)₂Cl₂ /1mol  Pt(NH₃)₂Cl₂ ) =7.3g

7.3 grams of cisplatin will be formed.