sc14, quantative analysis (paper 1)

Question 1

what is the yield

Answer 1

the mass of a product made in a chemical process

Question 2

what are the two main rules in any chemical reaction

Answer 2

• no atoms are gained or lost
• the total mass stays the same

Question 3

what is the theoretical yield

Answer 3

for a given mass for a limiting reactant, you can make only a maximum mass of a product

Question 4

what is the actual yield

Answer 4

the mass of the product that you really get at the end of a chemical process

Question 5

true or false: the actual yield is always less than the theoretical yield

Answer 5

true

Question 6

true or false: the actual yield is always more than the theoretical yield

Answer 6

false

Question 7

how do you calculate the percentage yield

Answer 7

(actual yield / theoretical yield) x 100

Question 8

true or false: a higher percentage yield means more mass is made

Answer 8

true

Question 9

true or false: a lower percentage yield means less mass is made

Answer 9

true

Question 10

true or false: a higher percentage yield means less mass is made

Answer 10

false

Question 11

true or false: a lower percentage yield means more mass is made

Answer 11

false

Question 12

what are the three main reasons for now obtaining the theoretical yield

Answer 12

• incomplete reactions
• side reactions
• practical losses

Question 13

what does a complete reaction mean in terms of not obtaining the theoretical yield

Answer 13

reaction hasn’t finished or reached equilibrium

Question 14

what does a side reaction mean in terms of not obtaining the theoretical yield

Answer 14

competing/unwanted reactions can cause by-products to be mae

Question 15

what does a practical loss mean in terms of not obtaining the theoretical yield

Answer 15

losses during purification (e.g filtration) or transfers (e.g liquid left behind in containers)

Question 16

what is meant by the atom economy

Answer 16

a way of measuring the number of atoms wasted when making a substance

Question 17

how do you calculate atom economy

Answer 17

(total Mr of desired products/total Mr of all products) x 100

Question 18

what does a 100% atom economy mean

Answer 18

all atoms in the reactants can be converted to the desired products

Question 19

what are the only two circumstances in which a 100% atom economy can happen in

Answer 19

• there is only one product (e.g manufacturing ammonia)
• all by-products are used (e.g as feedstock (reactants) for other products)

Question 20

how do you work out the titre

Answer 20

end reading - start reading

Question 21

what are concordant titres

Answer 21

titres identical or very close together (within 0.1cm3)

Question 22

what does the volume occupied by a gas depend on

Answer 22

• the number of particles present
• the tempurature of the gas
• the pressure of the gas

Question 23

what is the molar volume

Answer 23

the volume occupied by one mol of any gas at room tempurature and atmospheric pressure

Question 24

how do you work out the volume of gas

Answer 24

volume of gas (dm3 or cm3) = molar volume (dm3/mol or cm3/mol) x amount (mol)

Question 25

what is 1 dm3/mol in cm3/mol

Answer 25

1000

Question 26

what is 1 cm3/mol in dm3/mol

Answer 26

0.001