2/2 Moles

Question 1

Calculate molecular weight of H2O

Answer 1

Periodic table
1 H equals 1.0079 amu and 1 O weighs 15.99 amu so

2 x 1.0079 = 2.016 amu

1x15. 99 = 15.99 amu
2. 016 + 15.999 = 18.015 amu

Question 2

Formula mass of K2CO3

Answer 2

K= 2x 39.04) = 78.18
C = 1 x 12.01= 12.01
O = 16 (really 15.99) = 48
Total 138.2 amu

Question 3

Gram Formula Mass of lithium sulfate

LisO4

Answer 3

Li= 2 x 7 =14
S=1 x 32 = 32
O= 4 x 16 =64

Total 110 grams

Question 4

GFM of Na2CO3 10 H2O

Sodium carbonate deca hydrate

Answer 4

Na 2x 22= 44
C 1x12= 12
O 13x16= 208
H 1x20= 20

= 284

Question 5

What is formula for percent composition?

Answer 5

% comp= (mass part)/ (mass whole)

Question 6

What is percent composition of nitrogen in ammonium nitrate?

Answer 6

(28/80) X 100= 35%

Question 7

What is percent composition of H2O in calcium sulfate di hydrate

Answer 7

(36/172)x100= 20.93%

Question 8

What is a mole?

Answer 8

6.02 X 102️⃣3️⃣(23 rd power) of anything

Which is equal to 12 grams of 1️⃣2️⃣C (C-12 isotope) is equal to Avogadro’s number of carbon atoms.

Question 9

What is Avogadro’s number

Answer 9

Equal to a mole

6.02 X 102️⃣3️⃣

Question 10

What is the GFM of any substance is equal to

Answer 10

The mass of one mile of that substance

Question 11

What is Avogadro’s number equal to in regards to C-12?

Answer 11

12 grams of c-12 (1️⃣2️⃣C) equals a mole or Avogadro’s #

Question 12

GFM of H2O

Weight of a mole of water

Answer 12

Is 18

Takes 18 grams of H2O to have 1 mole of water molecules

Question 13

What is the mole calculation equation

Answer 13

of moles = (given mass)/(GFM)

Question 14

What is the mass of 2 moles of LiOH?

Answer 14

2= X/24
X= 48g

Question 15

What is the mass of 5 moles of barium cyanide?

Answer 15

Ba 137, CN 52
137+52= 189

5=X/189

189x5=945g

Question 16

What is the # of moles in 87.8 grams of di hydrogen sulfate?

Answer 16

X=87.8/98

x= .896

Question 17

Look at 2/5/16 for example of double and single replacement

Answer 17

Double replacement can occur if one is insoluble

Question 18

How many grams of C3H8 in 3.92 moles of it?

Answer 18

3.92= x/44
X= 172.48g

Question 19

How many moles does 22 g of carbon dioxide represent?

Answer 19

X= 22/44

X=0.5 moles

Question 20

How many molecules of glucose are in 1.97 moles of glucose?

Answer 20

1 mole 6.02 x 102️⃣3️⃣

1.97 mole = x
X= 1.185x102️⃣4️⃣

Question 21

How many water molecules are there in 5.5 moles of water?

Answer 21

5.5 moles x 6.02x102️⃣3️⃣

3.31x102️⃣4️⃣ molecules

Question 22

How many moles are in 25 grams of water?

Answer 22

(25 g H2O/1) x (1 mol H2o/18 g H2o)

= 1.39 moles h2o

Question 23

What is the empirical formula?

Answer 23

Indicates the different types of elements in a molecule and the lowest whole-number ratio of each kind of atom in the molecule

Question 24

Given empirical CH2

Find the molecular

Answer 24

GFM is 42 amu for C3 H6

Question 25

C3H4 empirical

Answer 25

GFM of 121

121/40 =3.025

C9H12

Question 26

Which has more atoms?

8 g of He or 10 g of Ne

Answer 26

He 8g/4 = 2 moles

Ne 10g/30 = 0.5 moles

He had more atoms

Question 27

What do subscripts represent?

Answer 27

Moles

H2 means 2 moles of H atoms

CO2 means 1 mole of carbon and 2 moles of oxygen

2H2O= 2 moles of water. 4 moles of H atoms and 2 moles of oxygen atoms

Question 28

Mole ratio of ethane

Answer 28

2C2H6 + 7 O2 –> 4CO2 + 6H2O

Ratio (molar) of ethane to oxygen is 2:7

Molar ratio of oxygen to H2O produced is7:6

Question 29

Suppose 6 moles of H2 reacted with N2- how many moles of NH3 would be formed?

Answer 29

Original H2:NH3

3:2
6:x
3x=12
x=4

Question 30

N2 + 3H2

How many moles N2

Answer 30

Original N2 NH3
New

2.75 moles of NH3
2x/2= 2.75/2

= 1.38 moles oh NH3

Question 31

What is molecular weight vs formula weight?

Answer 31

Molecular weight refer to covalently bonded compounds

Formula weight refer to both ionic and covalent compounds