Chapter 10, Problem 1MCP

(a)

Interpretation Introduction

Interpretation:

Pentane has higher melting point than decane has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  Decane contains ten carbon atoms and twenty two hydrogen atoms.  As the molar mass increases, the London Dispersion forces become stronger and as a result melting and boiling points will also increase.  Therefore, the given statement is false.

(b)

Interpretation Introduction

Interpretation:

Pentane is a substituted hydrocarbon has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  The structure of pentane can be given as,

As seen from the above structure, there are no substituents present on the carbon chain.  Hence, the given statement is a false one.

(c)

Interpretation Introduction

Interpretation:

Pentane is a saturated hydrocarbon has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  The structure of pentane can be given as,

As there is only single bonds present between the carbon atoms in the entire molecule as shown above, pentane is a saturated hydrocarbon only.  The given statement is true.

(d)

Interpretation Introduction

Interpretation:

Pentane is nonpolar has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  The structure of pentane can be given as,

Pentane contains only carbon and hydrogen atom.  Therefore, this is a nonpolar molecule only.  Given statement is true.

(e)

Interpretation Introduction

Interpretation:

Pentane has structural formula of ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$ has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  It is a linear alkane.  Structural formula for pentane can be given as shown below,

Molecular formula of pentane is only ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$.  Hence, the given statement is false.

(f)

Interpretation Introduction

Interpretation:

Pentane has weak London Dispersion forces than octane has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  Octane contains eight carbon atoms and eighteen hydrogen atoms.  As the molar mass increases, the London Dispersion forces become stronger.  This means pentane will have weaker London dispersion forces than octane.  Hence, the given statement is true.

(g)

Interpretation Introduction

Interpretation:

Pentane is a gas at room temperature has to be indicated as true or false.

Explanation of Solution

Alkanes with one to four carbon atoms are gases at room temperature, and alkanes with five to seventeen carbon atoms are colorless liquids at room temperature.  Pentane contains five carbon atoms in its skeleton.  Hence, pentane is a liquid at room temperature.  Therefore, the given statement is false.

(h)

Interpretation Introduction

Interpretation:

Pentane has only carbon‑carbon single bonds and carbon‑hydrogen single bonds has to be indicated as true or false.

Explanation of Solution

Pentane contains five carbon atoms and twelve hydrogen atoms.  The structure of pentane can be given as,

As there are no multiple bonds present in the above structure, pentane contains only single bonds between carbon and carbon, and carbon and hydrogen.  Therefore, the given statement is true.

(i)

Interpretation Introduction

Interpretation:

Per mol of Pentane requires $\text{8}\text{mol}$ of oxygen for complete combustion has to be indicated as true or false.

Explanation of Solution

Pentane has a molecular formula as ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$.  Alkanes on complete combustion produces carbon dioxide, water, and heat energy.  The chemical equation can be given as,

    ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}\text{+}{\text{O}}_{\text{2}}\stackrel{}{\to }{\text{CO}}_{\text{2}}\text{+}{\text{H}}_{\text{2}}\text{O}\text{+}\text{heat}\text{energy}$

Balanced chemical equation for the complete combustion of pentane can be given as,

    ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}\text{+}8{\text{O}}_{\text{2}}\stackrel{}{\to }5{\text{CO}}_{\text{2}}\text{+}6{\text{H}}_{\text{2}}\text{O}\text{+}\text{heat}\text{energy}$

As from the above equation it is understood that one mol of pentane requires eight mol of oxygen for complete combustion, the given statement is true.

(j)

Interpretation Introduction

Interpretation:

Pentane is a structural isomer of 2-methylpropane has to be indicated as true or false.

Explanation of Solution

Pentane has a molecular formula as ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$.  2-methylpropane has a molecular formula of ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$.  Structural isomers have same molecular formula but different connectivity of the atoms.  As they both do not have the same molecular formula, they are not structural isomers.  Therefore, the given statement is false.

(k)

Interpretation Introduction

Interpretation:

Pentane on reaction with $\text{HBr}$ produces 1-bromopropane, 2-bromopropane, and 3-bromopropane has to be indicated as true or false.

Explanation of Solution

Pentane is a saturated hydrocarbon.  It undergoes only substitution reaction and not addition reactions.  Pentane does not undergo reaction with hydrogen bromide to form 1-bromopropane, 2-bromopropane, and 3-bromopropane.  Therefore, the given statement is false.