Unit 1:3 (pt 1)

Question 1

Find the percentage mass

Answer 1

1. Find Mr of compound
2. Find Mr of the element
3. %= 1st step/ 2nd step x 100

Question 2

Using ratio

If 350g of A produces 600cm3 of B. How much B will be produced from 175g of A.

Answer 2

1. Ratio = A:B
   350g : 600cm3
   175g: Xcm3

2.Put X on top right side
175:X
350:600

3. Rearrange
   (175x600)/350 = X

Question 3

Figure out how many particles are in compounds / number of molecules

Answer 3

Number of moles x avogadro’s constant (6.02x10^23)

Question 4

Moles,mass, Mr formula

Answer 4

Mass
n x Mr

Question 5

Number of atoms in Xg

Answer 5

number of molecules x number of atoms in compound

Question 6

Calculations Involving Reacting Masses

Answer 6

1. Calculate the number of moles
2. Look at the ratio
3. calculate the mass

Question 7

Empirical Formula

Answer 7

1. Mass (g) of each element
2. Calculate number of moles
3. Divide by the smallest

Question 8

Molecular Formula

Answer 8

actual ratio of atoms in the molecule

The Mr must be the same as the molecule’s actual Mr

Question 9

Determination of xH2O

Answer 9

1. Calculate the moles of anhydrous compound
2. Calculate the moles of H2O lost.
3. Ratio
   moles of H2O lost / moles of anhydrous compound

Question 10

Percentage Yield equation

Answer 10

% = (actual yield/ theoretical yield) x 100

Question 11

Actual yield

Answer 11

mass in grams of the purified product after it has been dried

Question 12

Theoretical yield

Answer 12

What should be produced for a 100% yield

Question 13

Why can’t percentage yields always be 100%?

Answer 13

The reaction is reversible
Filtration
Transferring liquids
Unexpected reactions

Question 14

Atom economy equation

Answer 14

%atom economy = (Mr of useful products/ Mr of all reactants) x 100

Question 15

Reasons for good and bad atom economy

Answer 15

> HIgh a.e is better for profits and environment.
making lots of waste=problem
low a.e use resources quickly, produce lot of waste materials that need to be disposed. = unsustainable, raw materials run out.
low a.e aren’t profitable
raw materials = expensive
waste products expensive to remove
more than 1 way to create a product = find a reaction that gives useful by-products
highest a.e = ones with 1 product

Question 16

mol dm-3 to g dm-3

Answer 16

mol dm-3 — xMr —-> g dm-3
<—-/Mr—-

Question 17

Moles equation with dm-3

Answer 17

n (mol dm-3) = mass (g dm-3)
Mr (g mol-1)

Question 18

cm3 to dm3

Answer 18

x10-3
cm3 —-/1000—> dm3
<—-x1000—

Question 19

moles, volume, concentration equation

Answer 19

n = V (dm3) x C (mol dm-3)

n
c,v

Question 20

Definition of isotope

Answer 20

Atoms of the same element with the same number of protons and electrons but a different number of neutrons

Question 21

Definition of relative atomic mass (Ar)

Answer 21

The average mass of one atom of the element relative to 1/12 of the mass of an atom of carbon-12

Question 22

Definition of Relative isotopic mass

Answer 22

The mass of one atom of an isotope relative to 1/12 the mass of one atom of carbon-12

Question 23

Definition of a mole

Answer 23

The amount of substance in grams which has the same number of particles as there are atoms in 12g of carbon-12

Question 24

Definition of empirical formula

Answer 24

Simplest whole number ratio of atoms in a compound