Chemical Reactions Quiz: MCQ Exam!

The formula C12H22O11 represents a molecule of sucrose, which is a disaccharide made up of 12 carbon atoms. Therefore, the correct answer is 12.

The total amount of C and O in the products is 11 grams because the question states that the reactants include 7 grams of C and 4 grams of O. When these reactants undergo a chemical reaction, they will combine to form products. Since the reactants are completely consumed in the reaction, the total amount of C and O in the products will be equal to the sum of the amounts in the reactants, which is 7 grams + 4 grams = 11 grams. Therefore, the correct answer is 11 grams.

When iron combines with oxygen to form iron oxide, the reactants involved in the chemical reaction are iron and oxygen. Iron reacts with oxygen to produce iron oxide.

Water freezing is a physical change because it involves a change in the state of matter from a liquid to a solid. The molecules in water slow down and come closer together as the temperature decreases, forming a solid ice. The chemical composition of water remains the same during this process, making it a physical change rather than a chemical reaction.

A chemical reaction can be identified by the production of a different substance. This means that the reactants, which are the substances undergoing the reaction, combine and rearrange their atoms to form new substances with different chemical properties. This change in composition is a key characteristic of chemical reactions and distinguishes them from physical changes, such as changes in state or the formation of water.

To balance a chemical equation, you should change only the coefficients. Coefficients are the numbers that are placed in front of the chemical formulas to balance the number of atoms on both sides of the equation. By adjusting the coefficients, you can ensure that the same number of atoms of each element is present on both sides of the equation, maintaining the law of conservation of mass. Changing the subscripts would alter the chemical formula, which would represent a different compound altogether. The location of the arrow represents the direction of the reaction and does not affect the balancing of the equation.

In the given equation, 2H2 + O2 -> 2H2O, the coefficient in front of O2 is 1. This means that there is only one molecule of O2 involved in the reaction. Since each molecule of O2 contains two oxygen atoms, the total number of oxygen atoms in the product (2H2O) is also 2.

The given answer, C + O2 --> CO2, is a chemical equation because it represents a chemical reaction between carbon (C) and oxygen (O2) to form carbon dioxide (CO2). In a chemical equation, the reactants are written on the left side of the arrow and the products are written on the right side. In this equation, C and O2 are the reactants, and CO2 is the product. The arrow indicates the direction of the reaction, showing the transformation of the reactants into the products.

The arrow in a chemical equation indicates that a reaction is happening. It shows the direction in which the reactants are transforming into products. The arrow points from the reactants to the products, indicating the flow of the reaction.

To balance the equation Ag + O2 --> Ag2O, you need to ensure that the number of each type of atom is the same on both sides of the equation. By adding a 4 in front of Ag and a 2 in front of Ag2O, you have balanced the equation. This is because now there are 4 atoms of Ag on both sides and 2 atoms of O on both sides, resulting in a balanced equation.

Lavoisier was the first to determine that the masses of the reactants and products must be the same. He conducted experiments on chemical reactions and observed that no mass was gained or lost during the process. This led him to propose the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Lavoisier's work laid the foundation for modern chemistry and our understanding of the conservation of mass in chemical reactions.

When balancing an equation by changing subscripts, you are altering the chemical formula of the compound. This means that you are changing the arrangement and type of atoms in the compound, thus changing its identity. The number of molecules of the product, the atomic number, and the mass of the reactants may be affected by balancing the equation, but the primary change is the identity of the compound itself.