We don't have the passage. A random sampling of surfactant uses includes:
removal of oily materials from objects (clothes and dishes)
forms remarkable structures called bubbles
Assists in forming emulsions (e.g., mayonaise and paints)
Explanation:
The structure of a surfactant makes one end of a molecule hydrophilic and the other end hydrophobic. In water, they self-assemble into micelles, an arrangement in which the hydrophobic ends align towards the center, and the hydrophilic ends are pointed outwards to the water. This self-assembly is apparant when bubbles are made. The molecules quickly align themselves such that the hyrophilic ends are oriented inwards towards a thin layer of water and the hydrophobic ends are pointed outward to the air. This arrangement allows a mono-molecular sphere of water molecules to remain stable enough to float, reflect light, and please. These same properties allow the inverse to occur. Soap molecules surround a hydrophobic mass (e.g., the hamburger grease on your shirt) and solubilize it into small micelles which are then carried away in the surrounding water.
The answer is (3) The average velocity of the gas molecules increases. In the closed rigid cylinder, the volume of the gas and number of gas molecules will not change. The number of collision will increase.
In this case, we are evidencing a simple displacement reaction wherein the cobalt is able displace the hydrogen to produce cobalt (II) nitrate and gaseous hydrogen as a result of cobalt's higher activity: