Chapter 3 Part 1 Stoichiometry

Question 1

Ream of paper =

Answer 1

500 sheets

Question 2

Avogadro’s Number is?

Answer 2

1 mole = 6.02 X 10^23 things (atoms or
molecules)

Question 3

1 mole implies 2 things:

Answer 3

1) 6.02 x 10^23 atoms of an element

&

The atomic mass of an element in grams

Question 4

1 mole = how many atoms ?

Answer 4

6.02x10^23 atoms

Question 5

1 mole = what in grams?

Answer 5

The atomic mass in grams

Question 6

1 mole of Ba = how many atoms of Ba

Answer 6

6.02x10^23 atoms

Question 7

1 mole of Ba = what atomic mass?

Answer 7

137.3g Ba

Question 8

How many atoms of H are in 1.0 mole of H2O?

Answer 8

1 mol H2O x 2 mol H atoms 6.02x10^23
——————— x —————
1 mole H2O 1 mol H atom

= 1.2 x 10^24 atoms

Question 9

How many moles of phosphorus are in 70.0g of P?

Answer 9

Grams given / grams per mol = total mols

70.0g P x 1 mol P
———— = 2.26 mol P
31.0g

Question 10

The sum of the atomic masses of all atoms in the molecule is called the?

Answer 10

Molecular mass (weight)

Question 11

What is the Atomic mass of Vitamin C?

Answer 11

C6H8O6 =
C= 12.0(6)
H= 1.0(8)
O= 16.0(6)

= 176 amu (atomic mass units)
= 1 mole of Vitamin C

Question 12

What is usually the first step in calculating molecular problems ?

Answer 12

Total the molecular mass (weight)

Question 13

How many moles of Vitamin C are in 8.36*10^1g of Vitamin C?

Answer 13

Grams given / grams per mol

8.36*10^1g VC x 1 mol VC
————- = .475 mol
176g VC

Question 14

How many Grams of Vitamin C are in 1.73 mol of Vitamin C?

Answer 14

Moles given x grams per mol

1.73 mol VC x 176g
————- = 304g VC
1 mol VC

Question 15

How many H atoms are in 33.3g of Urea?
(NH2)2CO2

Answer 15

Mols given x mols of H x 6.02*10^23

33.3g Urea x 1 mol x 4mol Hx 6.02*10^23
———
60g/mole

= 1.34x10^24 H atoms

Question 16

% composition by mass is calculated how?

Answer 16

Grams of element / total grams *100

Question 17

Molecular Formula =

Answer 17

Actual # of atoms in a compound

Question 18

Empirical Formula =

Answer 18

Simples whole # ratio of atoms in a formula

Question 19

Sample contains only nitrogen and oxygen. The compound contains 30.5% of nitrogen what is the empirical formula??

Answer 19

That means 69.5 % O

30 to 69 is a 2 to 1 ratio

Question 20

If the molar mass of the compound is 92.0 g what is the molecular formula?

Answer 20

Divide grams given by the grams per mol of compound given, then multiply the
92.0g /46 g =2 then multiply the subscripts by that number

Question 21

Question 22

Things that can change you perfect yield

Answer 22

Spills
Splattering
Transfer errors
Excessive moisture

Question 23

% yield =

Answer 23

actual yield / theoretical (100%) *100

Question 24

Answer 24