Mass Relationships in Chemical Reactions

Mass Relationships in Chemical Reactions

Chemical Equations -

Menggambarkan senyawa kimia yang terlibat dalam reaksi kimia

Example: Calcium metal will react with liquid water to form solid calcium hydroxide and hydrogen gas. Ca(s) + 2 H2O(l )



Ca(OH)2(s) + H2(g)

Reactants

Products

States of matter in chemical equations: Solid = (s) Liquid = (l ) Gas = (g) Aqueous solution = (aq)

Chemical Equations -

Menggambarkan senyawa kimia yang terlibat dalam reaksi kimia

Example: Calcium metal will react with liquid water to form solid calcium hydroxide and hydrogen gas. 4 H atoms

Ca(s) + 2 H2O(l ) 1 Ca atom

2 H atoms 

2 H atoms = 4 H

+ Ca(OH)2(s) + H2(g)

1 Ca atom 2 O atoms

2 O atoms

Law of Conservation of Matter - Introduced in the 18 th century by French scientist Antoine Lavoisier. States that the amount of matter in the universe is finite and matter can neither be created or destroyed. • Therefore, if you start a reaction with 100 g of reactants, there must be 100 g of product after the reaction.

Chemical Equations -

Menggambarkan senyawa kimia yang terlibat dalam reaksi kimia

Example: Calcium metal will react with liquid water to form solid calcium hydroxide and hydrogen gas.

Ca(s) + 2 H2O(l )



Ca(OH)2(s) + H2(g)

Stoichiometric Coefficient

Stoichiometry - The relationship between the quantities of chemical reactants and products. Stoichiometric Coefficient - Suatu perbandingan dimana molekul satu zat bereaksi dengan molekul zat yang berbeda membentuk suatu zat lain

Chemical Equations -

Menggambarkan senyawa kimia yang terlibat dalam reaksi kimia

Example: Hot iron metal will react with chlorine gas to form solid iron(III) chloride.

A. Write the balanced chemical equation for this reaction. Be sure to identify the physical states of each reactant and product. B. What are the stoichiometric coefficients in this equation?

Chemical Equations -

Menggambarkan senyawa kimia yang terlibat dalam reaksi kimia

4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) This equation means 4 moles of Al + 3 moles of O 2 ---give---> 2 moles of Al2O3

Balancing Chemical Equations 1. Tulis formula yang benar untuk reaktan di sisi kiri dan rumus yang benar untuk produk di sisi kanan dari persamaan. Ethane reacts with oxygen to form carbon dioxide and water C2H6 + O2

CO2 + H2O

2. Mengubah angka di depan formula (koefisien) untuk membuat jumlah atom setiap unsur sama pada kedua sisi persamaan. Jangan mengubah subscript. 2C2H6

NOT

C4H12 3.7

Balancing Chemical Equations 3. Mulailah dengan menyeimbangkan elemen-elemen yang muncul hanya satu dalam reaktan dan produk. C2H6 + O2 2 carbon on left C2H6 + O2 6 hydrogen on left C2H6 + O2

CO2 + H2O

start with C or H but not O

1 carbon on right

multiply CO2 by 2

2CO2 + H2O 2 hydrogen on right 2CO2 + 3H2O

multiply H2O by 3 3.7

Balancing Chemical Equations 4. Seimbangkan elemen-elemen yang muncul dalam dua atau lebih reaktan atau produk. C2H6 + O2 2 oxygen on left

2CO2 + 3H2O

multiply O2 by

7 2

4 oxygen + 3 oxygen = 7 oxygen (3x1) on right (2x2)

C2H6 + 7 O2 2

2CO2 + 3H2O

2C2H6 + 7O2

4CO2 + 6H2O

remove fraction multiply both sides by 2

3.7

Balancing Chemical Equations 5. Periksa untuk memastikan bahwa Anda memiliki jumlah yang sama setiap jenis atom di kedua sisi persamaan. 2C2H6 + 7O2

4CO2 + 6H2O

4 C (2 x 2)

4C

12 H (2 x 6)

12 H (6 x 2)

14 O (7 x 2)

14 O (4 x 2 + 6)

3.7

Balancing Chemical Equations Periksa untuk memastikan bahwa Anda memiliki jumlah yang sama setiap jenis atom di kedua sisi persamaan. 2C2H6 + 7O2

4CO2 + 6H2O

Reactants 4C 12 H 14 O

Products 4C 12 H 14 O

3.7

Mass Changes in Chemical Reactions

1. Write balanced chemical equation 2. Convert quantities of known substances into moles 3. Use coefficients in balanced equation to calculate the number of moles of the sought quantity 4. Convert moles of sought quantity into desired units

3.8

Methanol burns in air according to the equation 2CH3OH + 3O2

2CO2 + 4H2O

If 209 g of methanol are consumed, what mass of water is produced?

3.8

Limiting Reagents

6 green used up

3.9

Limiting Reagents

6 red left over

3.9

IV. Limiting Reactants Making Apple Pies

+ 5 apples



1 crust

1 apple pie

• How many apple pies can you make with 150 apples and 33 crusts? • Would you have any leftover apples or crusts and if so, how many?

IV. Limiting Reactants Chemical Reactions 2 CO(g) + O2(g)



2 CO2(g)

• How many CO2 molecules can be formed from four CO molecules and three O2 molecules?

• CO is the limiting reagent and O 2 is the excess reagent.

Container (#1) of N2(g) and H2(g).

Copyright© by Houghton Mifflin Company. All rights reserved.

18

Before and after the reaction.

Copyright© by

19

Container (#2) of N2(g) and H2(g).

Copyright© by Houghton Mifflin

20

Before and after the reaction.

Copyright© by Houghton Mifflin

21

Figure 9.2: A map of the procedure used in Example 9.7.

Copyright© by Houghton Mifflin Company. All rights reserved.

22

Do You Understand Limiting Reagents? In one process, 124 g of Al are reacted with 601 g of Fe 2O3 2Al + Fe2O3

Al2O3 + 2Fe

Calculate the mass of Al2O3 formed. g Al

mol Al

mol Fe2O3 needed

g Fe2O3 needed

OR g Fe2O3 124 g Al x

mol Fe2O3 1 mol Al 27.0 g Al

x

mol Al needed 1 mol Fe2O3 2 mol Al

Start with ____ g Al

x

g Al needed

160. g Fe2O3 =  _____ g Fe2O3 1 mol Fe2O3

need _____ g Fe 2O3

Have more _______ ( _____ g) so ____ is limiting reagent

3.9

Use limiting reagent (Al) to calculate amount of product that can be formed. g Al

mol Al

mol Al2O3

2Al + Fe2O3

124 g Al x

1 mol Al 27.0 g Al

x

1 mol Al2O3 2 mol Al

g Al2O3

Al2O3 + 2Fe

x

102. g Al2O3 =  _____ g Al2O3 1 mol Al2O3

3.9

Dalam suasana yang memungkinkan, asetilen (C 2H2) dan HCl bereaksi membentuk vinil klorida (C 2H3Cl). Senyawa ini digunakan dalam pembuatan plastic dan mempunyai sifat karsinogenik. Dalam suatu contoh 35,0 gram C 2H2 dicampur dengan 51,0 gram HCl. • Yang mana yang merupakan pereaksi pembatas? • Berapa gram C2H3Cl yang terbentuk? • Berapa gram pereaksi yang berlebih yang masih tersisa setelah reaksi selesai.

Methanol burns in air according to the equation 2CH3OH + 3O2

2CO2 + 4H2O

If 209 g of methanol are consumed, what mass of water is produced? grams CH3OH

moles CH3OH

molar mass CH3OH 209 g CH3OH x

moles H2O

grams H2O

molar mass coefficients H2O chemical equation

4 mol H2O 18.0 g H2O 1 mol CH3OH = x x 32.0 g CH3OH 2 mol CH3OH 1 mol H2O

3.8