SC14

Question 1

What is the theoretical yield of a chemical reaction ?

Answer 1

The theoretical yield is the maximum mass of product
expected from the reaction, using reacting masses.

Question 2

What is the practical yield of a chemical reaction ?

Answer 2

The actual yield is the mass of the product that is actually obtained
from a chemical reaction.

Question 3

What is the percentage yield of a chemical reaction ?

Answer 3

The percentage yield of a chemical reaction shows how much product
was actually made compared with the amount of product that was
expected

Question 4

What are the 3 main reasons why reactions do not give 100% yields?

Answer 4

Reaction may be incomplete

Transfer losses

unwanted side reactions

Question 5

What is Atom Economy?

Answer 5

a method of showing how efficiently a particular reaction makes use of the atoms in the reactants.

Question 6

What problems do the disposal of waste products causes?

Answer 6

• Unpleasant smell near the chemical factory/industry
• We have to treat them e.g. react with other substances to
  make them safe. This may be expensive
• Environmental problems such as: water pollution, burning
  them may release toxic or acidic gases in the atmosphere
• Social problems such as house prices will drop near the
  industry

Question 7

Why do scientists change reaction pathway even though the percentage yield is high

Answer 7

• A reaction can have a high percentage yield
  but a low atom economy, meaning that waste
  by-products are formed.

Question 8

How can scientists improve atom economy?

Answer 8

• One way to improve the atom economy is to
  find uses for the by-products of the reaction.

Question 9

What are some other factors scientists consider when choosing a reaction pathway?

Answer 9

energy consumption, rate of reaction, raw materials, and the conditions needed to produce high yield if the reaction reaches equilibrium

Question 10

What is the apparatus for titration?

Answer 10

Safety filler
pipette
burette
conical flask
beaker
stand

Question 11

Explain the titration method.

Answer 11

1. Rinse a burette with hydrochloric acid, then fill the burette with the acid making sure the jet below the tap is also full
2. Record the initial volume of the acid in the burette
3. Rinse a pippete with sodium hyroxide solution, then fill the pippette to the 25cm cubed mark and empty the solution into the conical flask
4. Add afue drops of methyle orange indicator the place the conical flask onto a white tile
5. Add the Acid into the sodium hydroxide while swirdling the flask and the sides of the flask should be rinsed with small amounts of distilled water in order to make sure all the acid is in the mixture, then add the acid drop by drop untill you rach the end point
6. Record the final colume of acid in the burette
7. Repeat apart from the initial rinsing untill concordant results are obtained

Question 12

What are the 3 uses of titration?

Answer 12

• concentration of pollutants in water
• check concentration of substances in the blood
• verify the concentration of manufacturer’s
  products