# Analysis of Rates of Reaction

## Rate Graphs 1

**What you need to know:**

How to calculate the reaction rate by finding the gradient of a reaction-time graph.

*There are two main ways to find the rate of a reaction*, using the **equation __above or finding the __gradient of a reaction rate graph**.

The **gradient __(‘slope’) of the graph tells you how __fast the reaction is.** The steeper the gradient, the faster the reaction! For this to work you need to make sure that time is on the x-axis.

Since the reaction rate is changing all the time, we need to pick a time to work out the reaction rate.

__Here is how to find the gradient (and therefore reaction rate): __

- Draw a__ tangent__ to the curve of where you want to find that rate of reaction.
- __Pick two points __on that tangent line.
- Work out the__ difference in the y-coordinates__ of the two points you picked.
- Work out the
**difference in the x-coordinates**of the two points you picked. **Divide the difference in y by the difference in x.**- This gives you the gradient, which is the rate of the reaction!

## Rate Graphs 2

**Here is how to find the gradient (and therefore reaction rate):**

- Draw a tangent to the curve of where you want to find that rate of reaction.
- Pick two points on that tangent line.
- Work out the difference in the y-coordinates of the two points you picked.
- Work out the difference in the x-coordinates of the two points you picked.
- Divide the difference in y by the difference in x.
- This gives you the gradient, which is the rate of the reaction!

**Worked example:**

## Reaction Rate Expeiments

**What you need to know:**

How to find the rate of reaction of the two experiments below.

**You will need to know two experiments and how to measure their rates of reaction:**

**Magnesium and hydrochloric acid:**

As you can see, you are reacting a solid with a liquid to produce a liquid and a gas.

You can measure the **rate of reaction by collecting the gas in a syringe and measuring the volume of gas that is produced.**

**Sodium thiosulfate and hydrochloric acid:**

As you can see, you are reacting a liquid with a liquid to produce __a liquid, a gas, a solid and a liquid. __

You can measure the rate of reaction by **timing how long it takes for the solution to become opaque (can’t see through it)**. *You can do this by placing the flask on a piece of paper with an x drawn on. You can time how long it takes until you can no longer see the x.*