Question 1

Hydrogen is the most abundant element in the universe. In what state does hydrogen behave as a metal rather than a nonmetal?

Accepted Answer

At extremely high pressures, such as those found in the core of gas giant planets like Jupiter.

Question 2

Which of the following is the most practical industrial method for large-scale hydrogen production?

Accepted Answer

Steam-hydrocarbon reforming

Question 3

The Haber process is a major industrial use of hydrogen. Which chemical is synthesized in this process?

Accepted Answer

Ammonia ($$\mathrm{NH_3$})$$

Question 4

Which equation correctly represents the highly exothermic combustion of hydrogen?

Accepted Answer

$$\mathrm{H_2$(g) + \frac{1}{2}O_2$(g) \rightarrow H_2O(g)}$$ 
$$\Delta H^\circ = -242\ \mathrm{kJ/mol}$$

Question 5

Which of the following is a disadvantage of using hydrogen as a fuel compared to hydrocarbons like octane?

Accepted Answer

Hydrogen is less energy-dense by volume under normal conditions.

Question 6

Hydrogen can behave like both an alkali metal and a halogen. Which reaction demonstrates hydrogen acting as a halogen?

Accepted Answer

$$\mathrm{2Na(s) + H_2$(g) \rightarrow 2NaH(s)}$$

Question 7

Which of the following is a real-world application of hydrogenation reactions?

Accepted Answer

Converting vegetable oils into margarine and shortening

Question 8

What is a significant safety concern associated with the use of hydrogen as a fuel, as illustrated by the Hindenburg disaster?

Accepted Answer

Hydrogen is highly flammable and can cause explosive fires.

Question 9

Which property is NOT characteristic of alkali metals?

Accepted Answer

High melting points

Question 10

What is the primary source of sodium for industrial extraction?

Accepted Answer

Rock salt (NaCl) deposits

Question 11

Which process is used to extract sodium metal from sodium chloride?

Accepted Answer

Electrolysis of molten NaCl

Question 12

Which of the following is a common use of alkali metal compounds?

Accepted Answer

Table salt for food seasoning

Question 13

What is the balanced equation for the reaction of sodium with water?

Accepted Answer

$$\mathrm{2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2$(g)}$$

Question 14

Which of the following best explains why alkali metals must be stored under oil?

Accepted Answer

They react rapidly with moisture and oxygen in air.

Question 15

A transition metal hydride is being considered for hydrogen storage in fuel cell vehicles. What property makes these hydrides useful for this application?

Accepted Answer

They can reversibly absorb and release hydrogen gas.

Question 16

Which of the following reactions demonstrates hydrogen acting as an alkali metal?

Accepted Answer

$$\mathrm{H_2$(g) + S(g) \rightarrow H_2S(g)}$$

Question 17

Which of the following is a disadvantage of producing hydrogen by electrolysis of water on an industrial scale?

Accepted Answer

It requires large amounts of electrical energy, making it expensive.

Question 18

Which of the following best describes the trend in reactivity of alkali metals with water as you move down the group?

Accepted Answer

Reactivity increases due to decreasing ionization energy.

Question 19

A student proposes using hydrogen as a fuel for cars to reduce carbon emissions. Which of the following is a valid concern about this proposal?

Accepted Answer

Most hydrogen is currently produced from fossil fuels, which still generates carbon emissions.

lecture 9 chem

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