Question

The following models illustrate chemical reactions between X (red atoms) and Y (blue atoms). The "?" mark in each frame represents the amount of unreacted starting material. Enter the answers as the number of starting materials and the type (i.e., 1Y, 2X, 3Y, or 2X2). Assume that molecules will not break down into atoms unless a chemical reaction occurs. Excess molecules will stay in molecular form. If there are no leftover reactants, enter a value of 0.

Answer 1

In stoichiometry, atoms in a chemical reaction are counted to ensure the conservation of mass. Unreacted starting materials are indicated by '?' and can be determined by balancing the reactants and products. If there are no leftovers, the answer is '0'.

Step-by-step explanation:

Understanding Stoichiometry and Chemical Equations

Stoichiometry is the practice of counting atoms and molecules to ensure mass conservation in a chemical reaction. In the chemical equation provided, 'X' represents red atoms and 'Y' represents blue atoms. The 'reactants' are substances that enter the reaction, found on the left side of the equation, and the 'products' are substances that result from the reaction, found on the right side. If a reactant does not completely react, this results in a '?', representing unreacted starting material or excess molecules. The stoichiometric coefficients (numbers placed in front of molecules in a chemical equation) indicate how many of each molecule are used. Multiplying these by the subscript numbers (which count atoms within a molecule) shows the total number of atoms involved.

To determine the amount of unreacted starting material, one should balance the equation by ensuring that the number of each type of atom on the reactants side matches the number on the products side. Any discrepancy indicates the leftover reactant material. As an example, if a reaction shows 2X + Y → XY + X, it means that one X atom is unreacted. This would be written as '1X'. If no atoms are left unreacted, we denote this as '0'.

Answer 2

The frames are shown below.

Answer:

Part 1: Starting material = 5X and 8Y, ? = 1X;

Part 2: Starting material = 4X₂ and 3Y₂, ? = 1X₂;

Part 3: Starting material = 4X₂ and 4Y₂, ? = 2X₂;

Part 4: Starting material = 2X₂ and 3Y₂X, ? = X.

Step-by-step explanation:

Part 1

Each ball represents one atom, thus there are 5X and 8Y as starting materials. In the products there's 4X and 8Y forming 4 Y₂X, so ? = 1X.

Part 2

In this case, there are presented X₂ and Y₂ because the atoms are joined together, so the starting material is 4X₂ and 3Y₂. In the product, there are 6 YX, so it reacts 3X₂ and 3Y₂, and ? = 1 X₂.

Part 3

As in part 2 the atoms are joined together, so there are 4X₂ and 4Y₂. In the product, there are 4Y₂X, so it reacts 2X₂ and 4Y₂, so ? = 2X₂.

Part 4

The starting material now is 2X₂ and 3Y₂X, the product is 3Y₂X₂, so it reacts 3Y₂X and 3/2 X₂, thus ? = 1X.