B15 Alcohols, alkanoic acids and esters Flashcards
What is the functional group for an alcohol?
hydroxyl group, -OH
True or False: alcohols are named by using the prefix which indicates the total number of carbon atoms in the molecule plus the ending ‘-anol’.
true
Name the alcohol that has five carbon atoms.
pentanol
What is the general formula of an alcohol?
CnH2n+1OH
True or false: alcohol molecules are not polar
false. Alcohol molecules are polar due to the presence of the polar -OH group.
Alcohols are less volatile than their corresponding alkanes because ___________.
Because of the polar nature of the molecules. It causes the forces of attraction between the alcohol molecules to be stronger than between the non-polar alkane molecules.
Which of the following statements is true?
A. Polar solvents dissolve in polar solutes.
B. Non-polar solutes dissolve in polar solvents.
C. Polar solutes dissolve in polar solvents.
C. Polar solutes dissolve in polar solvents.
What products are formed during combustion of ethanol?
carbon dioxide and water
Write a chemical equation which summarises the complete combustion of ethanol.
C2H5OH (l) + 3O2 (g) ——> 2CO2 (g) + 3H2O (g)
True or False: Ethanol burns with a clear blue flame
True, because the ratio of carbon to hydrogen atoms in the molecule is low. All the carbon is converted to carbon dioxide- none remains to produce soot.
Complete the chemical equation:
2C2H5OH (l) + 2Na (s) —–> ?
2C2H5OH (l) + 2Na (s) —–> 2C2H5ONa (alc sol) + H2 (g)
What conditions are necessary for the dehydration of ethanol?
A. Heat and concentrated H2SO4
B. 5 atm pressure and 200 degrees Celcius
C. Heat
D. Concentrated H2SO4 and 170 degrees Celcius
D. Concentrated H2SO4 and 170 degrees Celcius
What product is formed when the elements of water are removed from an alcohol?
The corresponding alkene e.g. ethanol - water —-> ethene
During the breathalyser test to detect the presence of ethanol on a driver’s breath, the ethanol:
A. oxidises the green Cr3+ ion to the orange Cr2O7 ion
B. reduces the orange Cr2O7 ion to the green Cr3+ ion
C. reduces the green Cr3+ ion to the orange Cr2O7 ion
D. oxidises the orange Cr2O7 ion to the green Cr3+ ion
B. reduces the orange Cr2O7 ion to the green Cr3+ ion
True or False: Ethanol is oxidised to ethane when heated with acidified potassium manganate (VII) or acidified potassium dichromate (VI).
False: Ethanol is oxidised to ethanoic acid when heated with acidified potassium manganate (VII) or acidified potassium dichromate (VI).
Describe fermentation.
It is the chemical reaction in which carbohydrates are converted into ethanol by yeast under anaerobic conditions. Wine and rum are made by fermentation.
What is the general formula for alkanoic acids?
CnH2n+1COOH
The functional group of alkanoic acids is the _____ group, _____.
The functional group of alkanoic acids is the carboxyl group, - COOH.
True or False: Alkanoic acid molecules are polar.
True
Alkanoic acids are less volatile than their corresponding alkanes, because _____.
Because the forces of attraction between the polar alkanoic acid molecules are stronger than between the non-polar alkane molecules.
metals + alkanoic acid —–> ?
metals + alkanoic acid —-> salt + hydrogen
metal oxide + alkanoic acid —–> ?
metal oxide + alkanoic acid —–> salt + water
alkali + alkanoic acid —–> ?
alkali + alkanoic acid —-> salt + water
carbonates + alkanoic acid ——> ?
carbonates + alkanoic acid —-> salt + water+ carbon dioxide
sodium bicarbonate + alkanoic acid —-> ?
sodium bicarbonate + alkanoic acid —-> salt + water + carbon dioxide
Define esterification.
This is the process in which a carboxylic acid reacts with an alcohol to produce an ester and water.
What are the conditions necessary for esterification?
concentrated H2SO4 (catalyst, dehydrating agent) and heat
What is the general formula for esters?
CnH2n+1COOCxH2x+1
The functional group for esters is _______.
-COO-
True or False: Sugars and salts are esters.
False. Fats and oils are esters.
Summarise esterification using a word equation.
alkanoic acid + alcohol –conc. H2SO4 and heat—-> ester + water
butanol + propanoic acid —> ?
butanol + propanoic acid —-> butyl propanoate + water
Briefly describe acid hydrolysis of esters.
The ester is heated with an acid catalyst such as dilute hydrochloric or sulfuric acid.
Does this equation accurately summarise acid hydrolysis of ethyl ethanoate?
CH3COOC2H5 (l) + H20 (l) –conc. H2SO4, heat—-> CH3COOH (l) + C2H5OH (l)
Yes.
True or False: During alkaline hydrolysis, the ester is heated with sodium and potassium carbonate.
False. During alkaline hydrolysis, the ester is heated with sodium and potassium hydroxide solution.
Which of the following are true for saponification?
I. it is the alkaline hydrolysis of large esters
II. it produces water and a salt
III. it is used in the manufacture of soap
A. I only
B. I and III only
C. II only
D. I, II and III
B. I and III only
The ionic head is the ________ end of a detergent molecule and the tail is the ____________ end.
The ionic head is the hydrophilic end of a detergent molecule and the tail is the hydrophobic end.
State two ways in which a soap prepared from a fat or oil differs from a soapless detergent.
Soapy detergents do not lather easily in hard water, while soapless detergents lather in hard water. Soapy detergents are biodegradable, while soapless detergents are non-biodegradable.
