Alcohols

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Alcohols — Free MYP5 Chemistry Practice Questions

1QuestionALCOHOLS Functional Group (-OH) / General FormulaConcept Practice

2 marks~3 minCriterion A

The structural formula of ethanol is shown below, with a group of atoms highlighted.

State the name of the highlighted functional group and write its chemical formula. [1]

Explain why the presence of this functional group makes ethanol an alcohol rather than an alkane. [1]

Solutions

2QuestionALCOHOLS Functional Group (-OH) / General FormulaAssessment Practice

4 marks~6 minCriterion C

Experimental standard combustion enthalpies for four isomeric alcohols (molecular formula

C_4H_{10}O

) are given below.

Butan-1-ol:

-2676

kJ mol

^{-1}

Butan-2-ol:

-2660

kJ mol

^{-1}

2-Methylpropan-1-ol:

-2645

kJ mol

^{-1}

2-Methylpropan-2-ol:

-2630

kJ mol

^{-1}

Identify which alcohol does not follow the expected trend in combustion enthalpy as branching increases, and justify your answer with reference to the position of the

-

OH group and hydrogen bonding. [2]

Analyse how the position of the

-

OH group in butan-2-ol influences the strength of intermolecular forces and explain how this accounts for the deviation in its combustion enthalpy. [2]

Solutions

3QuestionNaming alcohols (IUPAC)Assessment Practice

6 marks~9 minCriterion D

Three alcohols are compared below.

Name	Methanol	Ethanol	Propan-1-ol
Structure	$CH_3OH$	$CH_3CH_2OH$	$CH_3CH_2CH_2OH$
$LD_{50}$ oral, rat (mg/kg)	5628	7060	1870
Common use	fuel/solvent	beverage/fuel	hand sanitiser/solvent

Explain why ethanol is considered safer than methanol for human consumption. In your answer, identify the metabolic products of each alcohol and link their toxicities to the enzymes involved. [2]

Evaluate the limitations of using

LD_{50}

data alone to establish safe human exposure limits for these alcohols. [2]

Discuss one significant limitation of relying exclusively on IUPAC naming to predict the health effects of a substance, using evidence from the data above to support your answer. [2]

Solutions

4QuestionCombustion of alcoholsAssessment Practice

3 marks~5 minCriterion B

The table below shows data for the complete combustion of four primary alcohols.

Alcohol	Carbon atoms	Oxygen consumed (mol)	Carbon dioxide produced (mol)
Methanol	1	1.5	1
Ethanol	2	3.0	2
Propanol	3	4.5	3
Butanol	4	6.0	4

State the trend in oxygen consumption as the number of carbon atoms increases. [1]

Write the general combustion equation for a primary alcohol of molecular formula

C_nH_{2n+2}O

, showing the stoichiometric coefficients in terms of

n

. [1]

Explain why each additional carbon atom in the alcohol chain requires exactly 1.5 mol of oxygen for complete combustion. [1]

Solutions

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