Grade 10 Chemistry Test

Explanation
Elements that lie on the left side of the periodic table are generally metals, not non-metals. The left side of the periodic table is known as the "s-block" and it includes the alkali metals and alkaline earth metals, which are all metals. Non-metals are typically found on the right side of the periodic table, in the "p-block". Therefore, the statement that elements on the left side of the periodic table are generally non-metals is incorrect.

Explanation
The light from a glow stick is a sign of a chemical change because it is produced by a chemical reaction. Glow sticks contain two separate compartments, one containing a hydrogen peroxide solution and the other containing a fluorescent dye. When the stick is bent, the compartments mix, causing the chemicals to react. This reaction produces light through a process called chemiluminescence, where energy is released in the form of light. Therefore, the light emitted from a glow stick is a result of a chemical change.

Explanation
Ionic bonds are formed when oppositely charged molecules are attracted to one another. This is because one atom donates electrons to another atom, resulting in the formation of positive and negative ions. These ions are then attracted to each other due to their opposite charges, forming an ionic bond. This type of bond is typically seen between metals and nonmetals, where the metal atom loses electrons to become a positive ion, and the nonmetal atom gains electrons to become a negative ion.

Explanation
False. In an anion, the number of electrons is greater than the number of protons, resulting in a negative charge. Anions are formed when an atom gains electrons during chemical reactions. Neutral atoms have the same number of protons as electrons.

Explanation
A supplier label for a hazardous chemical is required by law to have a hatched border because it helps to easily identify and distinguish hazardous chemicals from non-hazardous ones. The hatched border is a visual indicator that alerts individuals to the potential dangers associated with the chemical. It serves as a safety precaution and ensures that users are aware of the hazardous nature of the substance, allowing them to take appropriate measures to handle and store it safely.

Explanation
The mass number of an atom is the sum of its protons and neutrons. This is because protons and neutrons contribute to the mass of an atom, while electrons have negligible mass. Therefore, adding the number of protons and neutrons gives us the mass number of an atom.

Explanation
Nitrous oxide, N2O, is not an ionic compound. It is a covalent compound because it is composed of two nonmetals, nitrogen and oxygen, which share electrons to form bonds. Ionic compounds are often formed between a metal and a nonmetal, where electrons are transferred from the metal to the nonmetal to form ions. Since N2O does not fit this criteria, it is not an ionic compound.

Explanation
The observation that the substance burns brightly in the air provides information about its chemical properties. This suggests that the substance is likely flammable and reacts with oxygen in the air to produce a bright flame. This observation indicates that the substance has the potential to undergo a chemical reaction, specifically combustion, which is a characteristic of certain chemical compounds.

Explanation
Silicon would have atoms with the same number of outer electrons as carbon atoms. Both carbon and silicon belong to Group 14 of the periodic table, which means they have 4 valence electrons. Valence electrons are the electrons in the outermost energy level of an atom, and they determine the chemical properties of an element. Since both carbon and silicon have 4 valence electrons, they have the same number of outer electrons.

Explanation
Sodium citrate is a compound consisting of sodium ions and citrate ions. While the sodium ions are not part of molecules, the citrate ion itself is a molecular ion composed of carbon, hydrogen, and oxygen atoms covalently bonded. The entire sodium citrate compound in its typical usage in chemistry is often considered a molecular entity due to the presence of the citrate molecule. Methane is a clear example of a molecular compound. It is composed of one carbon atom and four hydrogen atoms covalently bonded together, forming a molecule. Solid sodium citrate and CH4​ gas (methane) are composed of molecules, with methane being the most straightforward example of a molecular compound. Sodium citrate, though ionic in part, includes a citrate ion which behaves as a molecular ion.

Explanation
Seawater would be the best conductor of electricity among the given options. This is because seawater contains a higher concentration of dissolved salts and minerals compared to pure water, tap water, or freshwater from a lake. These dissolved ions, such as sodium and chloride, act as conductors of electricity, allowing the flow of electric current more easily through seawater than through the other options.

Explanation
The correct chemical formula for the compound aluminum chloride is AlCl3. In this compound, aluminum has a +3 charge and chlorine has a -1 charge. To balance the charges, three chlorine atoms are needed for every one aluminum atom, resulting in the formula AlCl3.

Explanation
The correct chemical formula for the compound copper (II) fluoride is CuF2. In this compound, copper has a charge of +2 (as indicated by the Roman numeral II in parentheses) and fluoride has a charge of -1. To balance the charges, two fluoride ions are needed for every copper ion, resulting in the formula CuF2.

Explanation
The correct name for the compound K2O is Potassium Oxide. This is because the compound consists of two potassium atoms (K2) and one oxygen atom (O), resulting in the formula K2O. According to the rules of chemical nomenclature, the name of the compound is derived from the names of its constituent elements, with the metal (potassium) coming first followed by the non-metal (oxygen) with the suffix "-ide". Therefore, Potassium Oxide is the appropriate name for the compound K2O.