1. **State the problem:** We need to find the mass of chemical B required when 1.4 g of chemical A is used, based on the graph showing a linear relationship between the masses of chemicals A and B. 2. **Identify the relationship:** The graph is a straight line passing through the origin (0,0) and approximately the point (4, 3.4). This suggests a direct proportionality between mass of A and mass of B. 3. **Write the formula:** Since the line passes through the origin, the relationship can be written as $$y = kx$$ where $y$ is the mass of chemical B, $x$ is the mass of chemical A, and $k$ is the constant of proportionality. 4. **Calculate the constant $k$:** Using the point (4, 3.4), $$k = \frac{y}{x} = \frac{3.4}{4} = 0.85$$ 5. **Find the mass of chemical B when $x=1.4$ g:** $$y = 0.85 \times 1.4 = 1.19$$ 6. **Answer:** When 1.4 g of chemical A is used, approximately 1.19 g of chemical B is needed.