Molecules must collide in the correct orientation with enough energy to bond. Molecules need enough energy to collide and react.

14.51. (a) What factors determine whether a collision between two molecules will lead to a chemical reaction? The energy of collision and the orientation of the molecules when they collide determine whether a reaction will occur.

Particles must collide in order to react. The higher the concentrationof reactants, the greater the reaction rate. The physical state and structure of the reactants influences reaction rate. The higher the temperature, the greater the reaction rate.

When the concentration of all the reactants increases, more molecules or ions interact to form new compounds, and the rate of reaction increases. When the concentration of a reactant decreases, there are fewer of that molecule or ion present, and the rate of reaction decreases.

Now, since the rate constant increases, this implies that the rate of reaction increases with temperature. Regarding concentration: you are correct in that concentration affects the rate of reaction. However, a rate constant does not change according to concentration.

The rate is proportional to the concentration of a reactant. When you double the concentration the rate doubles. The rate is not affected by the concentration of a reactant. When you double the concentration the rate stays exactly the same.

Le Châtelier’s Principle states that a change in pressure, temperature, or concentration will push the equilibrium to one side of the chemical equation. So, if you manipulate the conditions to favour the product side, you increase the yield.

The reasons for this include:

• incomplete reactions, in which some of the reactants do not react to form the product.
• practical losses during the experiment, such as during pouring or filtering.
• side reactions (unwanted reactions that compete with the desired reaction)

How can you increase the yield of product from a reaction?

• Increase the temperature.
• Increase the concentration of reactants.
• Increase the surface area of the reactants.
• Use a catalyst.
• Remove the product as it’s formed.

High temperature and pressure produce the highest rate of reaction. However, this must be balanced with the high cost of the energy needed to maintain these conditions. Catalysts increase the rate of reaction without affecting the yield.

How to Improve Your Yield

1. Flame dry or oven dry flask and stirbar.
2. Use clean glassware.
3. Calculate and weigh reagent amounts accurately.
4. Purify reagents and solvents, if necessary.
5. Be sure your reactant is pure.
6. Rinse (3 times with reaction solvent) flasks and syringes used to transfer reactant and reagents.

The percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage. However, percent yields greater than 100% are possible if the measured product of the reaction contains impurities that cause its mass to be greater than it actually would be if the product was pure.

Usually, percent yield is lower than 100% because the actual yield is often less than the theoretical value. Reasons for this can include incomplete or competing reactions and loss of sample during recovery. This can happen when other reactions were occurring that also formed the product.

Theoretical yield can never be more than 100%, unless the molecular weight of the formed product is higher than that of the desired product. it not possible to get yield more than 100% in a chemical reaction as per the Mass laws.

Re: Theoretical vs Actual Yield The theoretical yield is always bigger because due to side reactions, impurities, etc. the actual yield will be less.

Theoretical yield will never be higher than actual yield. Theoretical yield is the result if the reaction is 100% efficient and there are no impurities or errors during the experiment. Theoretical yield represents the maximum yield.

Why Is Actual Yield Different from Theoretical Yield? Usually, the actual yield is lower than the theoretical yield because few reactions truly proceed to completion (i.e., aren’t 100% efficient) or because not all of the product in a reaction is recovered.

To calculate the theoretical yield, determine the number of moles of each reactant, in this case the sole reactant ethanol. Convert the 100 g to moles; the molecular weight of ethanol is 46 g/mole, therefore: Since there is only one reactant, it is also the limiting reagent.

Remember, the theoretical yield is the amount of product produced when the entire limiting product is used up, but then actual yield is the amount of product that is actually produced in a chemical reaction.