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

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.

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.