Correct Answer: D. Fe₂O₃

Explanation

Rust is a reddish-brown compound that forms on the surface of iron in the presence of oxygen and moisture. Its chemical formula is Fe2O3, indicating the presence of two iron atoms and three oxygen atoms in the compound.

Correct Answer: D. Addition reaction

Explanation

Alkanols can be formed from alkenes through an addition reaction. In this reaction, the carbon-carbon double bond of the alkene is broken, and a hydroxyl group (-OH) is added to one of the carbon atoms, resulting in the formation of an alcohol.

Correct Answer: A. 4

Explanation

In an alkene with six carbon atoms, there are 5 sigma (α) bonds (single bonds) between the carbon atoms. Additionally, there are 4 pi (π) bonds associated with the double bonds between the carbon atoms.

Correct Answer: B. CH\(_2\)O

Explanation

To determine the empirical formula, we first need to convert the percentages to moles by assuming a convenient mass for the sample. Let's assume we have 100 grams of the compound.

Mass of carbon = 40.00 grams

Mass of hydrogen = 6.67 grams

Mass of oxygen = 53.33 grams

Now, we calculate the moles of each element:

Moles of carbon = 40.00 g / molar mass of carbon = 40.00 g / 12.01 g/mol ≈ 3.33 mol

Moles of hydrogen = 6.67 g / molar mass of hydrogen = 6.67 g / 1.01 g/mol ≈ 6.60 mol

Moles of oxygen = 53.33 g / molar mass of oxygen = 53.33 g / 16.00 g/mol ≈ 3.33 mol

Now, we find the smallest whole-number ratio of the moles:

C ≈ 3.33 / 3.33 ≈ 1

H ≈ 6.60 / 3.33 ≈ 2

O ≈ 3.33 / 3.33 ≈ 1

Thus, the empirical formula is CH2O.

To determine the empirical formula, we first need to convert the percentages to moles by assuming a convenient mass for the sample. Let's assume we have 100 grams of the compound.

Mass of carbon = 40.00 grams

Mass of hydrogen = 6.67 grams

Mass of oxygen = 53.33 grams

Now, we calculate the moles of each element:

Moles of carbon = 40.00 g / molar mass of carbon = 40.00 g / 12.01 g/mol ≈ 3.33 mol

Moles of hydrogen = 6.67 g / molar mass of hydrogen = 6.67 g / 1.01 g/mol ≈ 6.60 mol

Moles of oxygen = 53.33 g / molar mass of oxygen = 53.33 g / 16.00 g/mol ≈ 3.33 mol

Now, we find the smallest whole-number ratio of the moles:

C ≈ 3.33 / 3.33 ≈ 1

H ≈ 6.60 / 3.33 ≈ 2

O ≈ 3.33 / 3.33 ≈ 1

Thus, the empirical formula is CH2O.

Correct Answer: D. The collisions of gas particles with the container walls

Correct Answer: D. Hematite

Explanation

Hematite is the principal ore of iron and is widely mined for the extraction of iron metal.

Correct Answer: B. Esterification

Explanation

When alkanoic acids react with alcohols in the presence of an acid catalyst, esterification occurs. This chemical reaction forms esters and water.

Correct Answer: A. The position of equilibrium shifts to the left

Explanation

When the temperature is decreased in a reversible reaction, the equilibrium shifts in the direction that produces heat (exothermic direction). For an exothermic reaction, this means the equilibrium position shifts to the left, favoring the reverse reaction.

Correct Answer: A. Pentane

Explanation

Crude oil is a mixture of hydrocarbons of various chain lengths. Pentane is one of the primary constituents of crude oil, and it belongs to the group of alkanes.

Correct Answer: B. Fluorine (F)

Explanation

Fluorine is a halogen that is a gas at room temperature and is pale yellow in color. Halogens are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Among these, only Fluorine and Chlorine are gases at room temperature, but Chlorine is greenish-yellow, not pale yellow.