Ques: Answer the following question given this paragraph: H2 + O2 H2O This is an example of a chemical equation, which is a concise way of representing a chemical reaction. The initial substances are called reactants, and the final substances are called products. Unfortunately, it is also an incomplete chemical equation. The law of conservation of matter says that matter cannot be created or destroyed. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products. If we count the number of hydrogen atoms in the reactants and products, we find two hydrogen atoms. But if we count the number of oxygen atoms in the reactants and products, we find that there are two oxygen atoms in the reactants but only one oxygen atom in the products. What can we do? Can we change the subscripts in the formula for water so that it has two oxygen atoms in it? No; you cannot change the formulas of individual substances because the chemical formula for a given substance is characteristic of that substance. What you can do, however, is to change the number of molecules that react or are produced. We do this one element at a time, going from one side of the reaction to the other, changing the number of molecules of a substance until all elements have the same number of atoms on each side. To accommodate the two oxygen atoms as reactants, let us assume that we have two water molecules as products:. Q: Initial substances are called reactants, and the final substances are called what? Choices: - exports - imports - reactors - products A:
Ans: products

Ques: Answer the following question given this paragraph: It is necessary to distinguish between the two types of covalent bonds in a C 2 H 4 molecule. A sigma bond ( bond) is a bond formed by the overlap of orbitals in an end-to-end fashion, with the electron density concentrated between the nuclei of the bonding atoms. A pi bond ( bond) is a bond formed by the overlap of orbitals in a side-by-side fashion, with the electron density concentrated above and below the plane of the nuclei of the bonding atoms. Figure below shows the two types of bonding in C 2 H 4 . The sp 2 hybrid orbitals are orange and the p z orbital is green. Three sigma bonds are formed by each carbon atom with its hybrid orbitals. The pi bond is the "second" bond of the double bond between the carbon atoms and is shown as an elongated blue lobe that extends both above and below the plane of the molecule, which contains the six atoms and all of the sigma bonds. Q: What term is used to describe a bond formed by the overlap of orbitals in an end-to-end fashion, with the electron density concentrated between the nuclei of the bonding atoms? Choices: - beta bond - lattice bond - rna bond - sigma bond A:
Ans: sigma bond

Ques: Answer the following question given this paragraph: A mycorrhiza (Greek for "fungus roots") is a symbiotic association between a fungus and the roots of a plant. In a mycorrhizal association, the fungus may colonize the roots of a host plant by either growing directly into the root cells, or by growing around the root cells. This association provides the fungus with relatively constant and direct access to glucose, which the plant produces by photosynthesis. The mycelia of the fungi increase the surface area of the plant's root system. The larger surface area improves water and mineral nutrient absorption from the soil. Q: A mycorrhiza refers to what kind of relationship between a fungus and the roots of a plant? Choices: - predator-prey - semantic - familial - symbiotic A:
Ans: symbiotic

Ques: Answer the following question given this paragraph: Chemical reactions are described using chemical equations. Q: How do we describe chemical reactions? Choices: - balanced reactions - equilibrium - atomic numbers - chemical equations A:
Ans:
chemical equations