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Chapter 19: Problem 90

Which of the following statement(s) is(are) true? a. The alkali metals are found in the earth's crust in the form of pure elements. b. Gallium has one of the highest melting points known for metals. c. When calcium metal reacts with water, one of the products is \(\mathrm{H}_{2}(\mathrm{~g})\) d. When \(\mathrm{AlCl}_{3}\) is dissolved in water, it produces an acidic solution. e. Lithium reacts in the presence of excess oxygen gas to form lithium superoxide.

Short Answer

Expert verified
The true statements are c and d. Statement c: When calcium metal reacts with water, one of the products is $\mathrm{H}_{2}(\mathrm{~g})$. Statement d: When $\mathrm{AlCl}_{3}$ is dissolved in water, it produces an acidic solution.

Step by step solution

01

Statement a: Alkali metals in earth's crust

Alkali metals are very reactive and are not found in nature in their pure elemental form. They are typically found as compounds or in mineral form. So, statement a is false.
02

Statement b: Melting point of Gallium

Gallium is a soft metal with a very low melting point of 29.76°C (85.57°F). It is not one of the highest melting points known for metals. Statement b is false.
03

Statement c: Reaction of calcium with water

Calcium reacts with water to form calcium hydroxide and hydrogen gas. The balanced chemical reaction is: \( \mathrm{Ca}(s)+ 2\mathrm{H}_{2}\mathrm{O}(l) \to \mathrm{Ca}(\mathrm{OH})_2(aq) + \mathrm{H}_{2}(g) \) So, statement c is true.
04

Statement d: Behavior of \(\mathrm{AlCl}_{3}\) in water

When aluminum chloride (\(\mathrm{AlCl}_{3}\)) dissolves in water, it undergoes hydrolysis to form aluminum hydroxide and hydrochloric acid. The balanced chemical reaction is: \( \mathrm{AlCl}_{3}(s) + 3\mathrm{H}_{2}\mathrm{O}(l) \to \mathrm{Al}(\mathrm{OH})_{3}(s) + 3\mathrm{HCl}(aq) \) The solution contains hydrochloric acid, which is acidic. Therefore, statement d is true.
05

Statement e: Lithium in the presence of excess oxygen

When lithium reacts with excess oxygen gas, it forms lithium peroxide, not lithium superoxide. The balanced chemical equation is: \( 2\mathrm{Li}(s) + \mathrm{O}_{2}(g) \to 2\mathrm{Li}_2\mathrm{O}_2(s) \) So, statement e is false. In conclusion, the true statements are c and d.

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Most popular questions from this chapter

Indium(III) phosphide is a semiconducting material that has been frequently used in lasers, light-emitting diodes (LED), and fiber-optic devices. This material can be synthesized at900. K according to the following reaction: $$\operatorname{In}\left(\mathrm{CH}_{3}\right)_{3}(g)+\mathrm{PH}_{3}(g) \longrightarrow \operatorname{InP}(s)+3 \mathrm{CH}_{4(g)$$ a. If \(2.56 \mathrm{L} \operatorname{In}\left(\mathrm{CH}_{3}\right)_{3}\) at 2.00 atm is allowed to react with \(1.38 \mathrm{L} \mathrm{PH}_{3}\) at \(3.00 \mathrm{atm},\) what mass of \(\operatorname{In} \mathrm{P}(s)\) will be produced assuming the reaction has an \(87 \%\) yield?b. When an electric current is passed through an optoelectronic device containing InP, the light emitted has an energy of \(2.03 \times 10^{-19} \mathrm{J} .\) What is the wavelength of this light and is it visible to the human eye? c. The semiconducting properties of InP can be altered by doping. If a small number of phosphorus atoms are replaced by atoms with an electron configuration of \([\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{4},\) is this n-type or \(\mathrm{p}\) -type doping?

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