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Chapter 20: Problem 98

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 \(\mathrm{H}_{2}(g) .\) d. When 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
Statements c, d, and e are true.

Step by step solution

01

Statement a

: Alkali metals are highly reactive and do not exist in their pure elemental form in the earth's crust. They are found as components in various compounds such as halides and oxides. Therefore, statement a is false.
02

Statement b

: Gallium has a relatively low melting point of about 29.8\(^\circ\)C (85.6\(^\circ\)F). There are many metals with much higher melting points, such as tungsten, which has the highest melting point for metals at around 3,422\(^\circ\)C (6,192\(^\circ\)F). So, statement b is false.
03

Statement c

: When calcium metal reacts with water, the balanced chemical reaction is: Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) As we can see from this reaction, one of the products is indeed hydrogen gas, H2(g). Therefore, statement c is true.
04

Statement d

: When aluminum chloride (AlCl3) is dissolved in water, it hydrolyzes to produce an acidic solution. The balanced chemical reaction is: AlCl3(s) + 3H2O(l) ↔ Al(OH)3(s) + 3HCl(aq) The HCl produced in this reaction generates an acidic solution. Hence, statement d is true.
05

Statement e

: When lithium reacts in the presence of excess oxygen gas, it forms lithium superoxide (LiO2). The balanced chemical reaction for this is: 2Li(s) + O2(g) → 2LiO2(s) Therefore, statement e is true. In conclusion, statements c, d, and e are true.

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Most popular questions from this chapter

What structural features do the molecules $\mathrm{P}_{4}, \mathrm{P}_{4} \mathrm{O}_{6},\( and \)\mathrm{P}_{4} \mathrm{O}_{10}$ have in common?

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