Chemistry $^{3}$ : Introducing inorganic, organic and physical chemistry

Andrew Burrows, John Holman, Andrew Parsons

Chapter 26 s-Block chemistry - all with Video Answers

Educators

Chapter Questions

Problem 1

Sodium can be used to prepare zirconium from $\mathrm{ZrCl}_{4}$. What mass of sodium is required to yield $1 \mathrm{~kg}$ of zirconium? (Section 26.1)

Rajesh S.

Numerade Educator

03:54

Problem 2

Identify the products and write balanced equations for the following reactions (Section 26.2):
(a) adding caesium to water,
(b) burning rubidium in an excess of air,
(c) heating lithium nitrate.

Pronoy S.

Numerade Educator

02:53

Use a Born-Haber cycle and the data below to explain why $\mathrm{NaCl}_{2}$ doosn't exist. Assume the ionic radius of $\mathrm{Na}^{2+}$ is the same as that for $\mathrm{Mg}^{2+}$. (Section 26.2)
lonic radii: $\mathrm{Mg}^{2+}, 72 \mathrm{pm} ; \mathrm{Cl}, 181 \mathrm{pm}$
$\Delta_{n} H^{\circ}(\mathrm{Na})=+108 \mathrm{~kJ} \mathrm{~mol}^{-1} \quad \Delta_{\alpha} H^{\circ}(\mathrm{Cl})=+121 \mathrm{~kJ} \mathrm{~mol}^{-1}$
$\Delta H(1)^{\ominus}(\mathrm{Na})=+496 \mathrm{~kJ} \mathrm{~mol}^{-1} \quad \Delta_{\mathrm{og}} \mathrm{H}(1)^{\bullet}(\mathrm{Cl})=-349 \mathrm{~kJ} \mathrm{~mol}^{-1}$
$\Delta H(2)^{\ominus}(\mathrm{Na})=+4562 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Rajesh S.

Numerade Educator

01:57

Problem 4

Predict which compound in each of the following pairs has the higher decomposition temperature: (a) $\mathrm{NaNO}_{3}$ and $\mathrm{KNO}_{3}$; (b) $\mathrm{LiH}$ and $\mathrm{KH}$; (c) $\mathrm{Li}_{2} \mathrm{CO}_{3}$ and $\mathrm{SrCO}_{3}$. Give reasons for your answer. (Section 26.2)

Crystal W.

Numerade Educator

07:16

Problem 5

A Group 1 metal, $M$, burns in air to produce $X$, which reacts with water to form Y. $M$ also reacts with water to form $Y$, giving off a combustible gas $Z$. When $Y$ is heated, it gives off steam to form $\mathrm{X}$. Identify M, X, Y, and Z. (Section 26.2)

Pronoy S.

Numerade Educator

Problem 6

Construct an enthalpy cycle for the decomposition of a Group 1 nitrate to an oxide. Using the Kapustinskii equation to estimate values of the lattice energies, calculate values for the decomposition of lithium nitrate to lithium oxide and potassium nitrate to potassium oxide, Use the calculated values to predict which of these nitrates decomposes to the oxide on heating.
(Section 26.2).
Values for ionic radii are given in Tables $6.4$ (p.286), $6.5$
(p.286), and $6.9$ (p.297).
The enthalpy change for the reaction
$$
2 \mathrm{NO}_{3}{ }^{-}(\mathrm{g}) \rightarrow \mathrm{O}^{2}-(\mathrm{g})+4 \mathrm{NO}(\mathrm{g})+3 \mathrm{O}_{2}(\mathrm{~g})
$$
is $+2160 \mathrm{~kJ} \mathrm{~mol}^{-1}$

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04:10

Problem 7

Which of the following pairs of Group 1 compounds would you expect to be more soluble in water? (Section 26.3)
(a) $\mathrm{LiNO}_{3}$ or $\mathrm{CsNO}_{3}$
(b) LIOH or RbOH
(c) $\mathrm{NaBr}$ or $\mathrm{CsBr}$.

Rajesh S.

Numerade Educator

01:54

Problem 8

Suggest how the crown ether below could be used to separate mixtures of $\mathrm{Li}^{+}$and $\mathrm{K}^{+}$. (Section 26.4)

Rajesh S.

Numerade Educator

Problem 9

Magnesium chloride is prepared by reacting sea water with $\mathrm{Ca}(\mathrm{OH})_{2}$ to precipitate $\mathrm{Mg}(\mathrm{OH})_{2}$, reacting this with hydrochloric acid, and then evaporating the solution slowly to give crystals of magnesium chloride. (Section 26.6)
(a) Write balanced equations for these reactions, ignoring any water of crystallization.
(b) A sample of $\mathrm{MgCl}_{2}$ obtained from this process contains $18.5 \%$ magnesium by mass. Assuming there are no impurities, how many molecules of water does the $\mathrm{MgCl}_{2}$ crystallize with?

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