*Question*
Answer the following question given this paragraph: Nitrates, salts of nitric acid, form when metals, oxides, hydroxides, or carbonates react with nitric acid. Most nitrates are soluble in water; indeed, one of the significant uses of nitric acid is to prepare soluble metal nitrates. Nitric acid finds extensive use in the laboratory and in chemical industries as a strong acid and strong oxidizing agent. It is important in the manufacture of explosives, dyes, plastics, and drugs. Salts of nitric acid (nitrates) are valuable as fertilizers. Gunpowder is a mixture of potassium nitrate, sulfur, and charcoal. The reaction of N2O3 with water gives a pale blue solution of nitrous acid, HNO2. However, HNO2 (shown in Figure 18.51) is easier to prepare by the addition of an acid to a solution of nitrite; nitrous acid is a weak acid, so the nitrite ion is basic in aqueous solution: NO 2 (aq) + H 3 O +(aq) HNO 2(aq) + H 2 O(l) Nitrous acid is very unstable and exists only in solution. It disproportionates slowly at room temperature (rapidly when heated) into nitric acid and nitric oxide. Nitrous acid is an active oxidizing agent with strong reducing agents, and strong oxidizing agents oxidize it to nitric acid. Q: What is a mixture of potassium nitrate, sulfur, and charcoal? Choices: - gasoline - cyanide - TNT - gunpowder A:
**Answer**
gunpowder

*Question*
Answer the following question given this paragraph: Ecological succession is the process in which a community changes through time. Primary succession occurs in an area that has never before been colonized. Secondary succession occurs in a formerly inhabited area that was disturbed. Q: What is the term for the process in which an area that has never before been colonized changes through time? Choices: - continuous succession - environmental succession - colony succession - ecological succession A:
**Answer**
ecological succession

*Question*
Answer the following question given this paragraph: Density is defined as the mass of an object divided by its volume. Propose a unit of density in terms of the fundamental SI units. Q: Density is defined as the mass of an object divided by its what? Choices: - size - liquid - growth - volume A:
**Answer**
volume

*Question*
Answer the following question given this paragraph: Visible Light Visible light is the narrow segment of the electromagnetic spectrum to which the normal human eye responds. Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules. The receivers or detectors of light largely utilize electronic transitions. We say the atoms and molecules are excited when they absorb and relax when they emit through electronic transitions. Figure 24.16 shows this part of the spectrum, together with the colors associated with particular pure wavelengths. We usually refer to visible light as having wavelengths of between 400 nm and 750 nm. (The retina of the eye actually responds to the lowest ultraviolet frequencies, but these do not normally reach the retina because they are absorbed by the cornea and lens of the eye. ) Red light has the lowest frequencies and longest wavelengths, while violet has the highest frequencies and shortest wavelengths. Blackbody radiation from the Sun peaks in the visible part of the spectrum but is more intense in the red than in the violet, making the Sun yellowish in appearance. Q: Visible light is the narrow segment of what, to which the normal human eye responds? Choices: - molecular spectrum - radio spectrum - phenomena spectrum - electromagnetic spectrum A:
**Answer**
electromagnetic spectrum