Stoichiometry *

Question 1

What is the equation linking mass, formula mass and moles?

Answer 1

no. of moles = mass / RFM

Question 2

What is the equation to work out the no. of moles of a gas?

Answer 2

no. of moles of gas = volume (dm3) / 24

Question 3

What does diatomic mean?

Answer 3

consisting of two atoms

Question 4

Give three diatomic elements?

Answer 4

oxygen, chlorine, hydrogen

Question 5

How do you convert from cm3 to dm3?

Answer 5

divide by 1000

Question 6

How do you find the volume of a gas?

Answer 6

volume = no. of moles x 24

Question 7

How do you calculate the percentage yield?

Answer 7

% yield = actual yield / theoretical yield x 100

Question 8

How do you calculate atom economy?

Answer 8

atom economy of reaction = RFM of useful products/ RFM of all products x 100

Question 9

What is the atom economy if there is only one product of the reaction?

Answer 9

100%

Question 10

What are the two ways of making ethanol?

Answer 10

1) by hydrating ethane with steam (using a catalyst)
2) produced by fermentation of yeast (using catalyst)

Question 11

What are the conditions needed for method 2 of producing ethanol? (fermenting yeast)

Answer 11

sugar in waterm yeast (catalyst) and temp of 30 to 40 degrees

Question 12

How do you calculate concentration?

Answer 12

concentration = number of moles / volume (dm3)

Question 13

What is titration?

Answer 13

adding one liquid to another in a measured way to determine the concentration of a solution

Question 14

What is a titre?

Answer 14

the volume added from the burette

Question 15

What is the method of titration using HCl and NaOH?

Answer 15

1) fill burette with HCl
2) Transfer 25cm3 of NaOH using a glass pipette into a conical flask
3) add a few drops of phenolphthalein indicator to the NaOH
4) carry out titration (adding the HCl from the burette into the conical flask until the indicator turns colourless (neutral))
5) repeat experiment 3 or 4 times to find concordant results (within 0.1cm3 of each other)