Mass to Mass Conversions

Mass to Mass Conversion only requires one more additional step from the stuff you've learned already.



Example:



???

http://www.youtube.com/watch?v=2Q8HtHItjxI

-Candace Chan

Mole to Mass & Mass to Mole

- questions may contain an amount of moles and ask you to determine the mass.
- Converting moles to mass only requires one additional step.


Steps:

1) Write the equations of the given formula
2) Balance the equations

Example:

Zn + HCl = ZnCl2 + H2

Then balance the equation

Zn + 2HCl = ZnCl2 + H2

then let's say the mole od zinc was 3.5, what is the mass of hydrogen?

3.5 mol x

multiply it over what you need over what you have!!

3.5 mol x  1   
                 1

Then you multiply it by the molar mass of the element you need, in this case, you need to find the molar mass of hydrogen. (remember the subscripts)

3.5mol x 1 x   2          =
               1   1 mol

 Multiply the whole equation and you get:

3.5 mol x 1  x   2    = 7 grams of hydrogen
                1    1 mol

Easy right?
Wait, we're not done yet...let's do the reverse.

How many moles are there in barium nitrate are consumed when 2.55 grams of silver chloride completely reacts?

First, remember to write the balanced equation:

Ba(NO3)2 + 2AgCl = BaCl2 + 2AgNO3

You do the reverse now, you use the molar mass of what you have. I repeat, what you have:

2.55 grams x 1 mol    x
                     143.3 g

Then multiply it by what you need over what you have!:

2.55 grams x 1 mol   x    1  =  0.00890 moles
                       143.3 g     2

http://www.youtube.com/watch?v=JIw_BmFZdhI
http://www.wisc-online.com/objects/ViewObject.aspx?ID=GCH4104

-Candace Chan

Mole to Mole Conversions

·         Coefficients in balanced equations tell us the number of moles reacted or produced

·         They can also be used as conversion factors

Example: 3X+Y=4Z

6 mol+2mol= 4Z

1.5 mol+0.5 mol= 1Z

6.15mol+2.05mol=4.1mol

v  WHAT YOU NEED OVER WHAT YOU HAVE

Ex: 7.2mol x 1/3

·         If 0.15 mol of methane are consumed in a combustion reaction, how many moles of CO₂ are produced?

1Ch₄+2O₂= 1CO₂+2H₂O

0.15mol x 1/1 = 0.15 mol of CO₂

·         How many moles of bauxite (Aluminum Oxide) are required to produce 1.8 mol of pure Aluminum?

2Al₂O₃= 4Al+3O₂

1.8 mol x 2/4 (what you need over what you have) = 0.9 mol of bauxide

·         When 1.5 mol of Copper reacts with Iron (II) Chloride, how many moles of Iron should be produced?

1Cl+1Fecl₂=1Fe+1CuCl₂

1.5 mol x 1/1 = 1.5 mol

http://www.youtube.com/watch?v=HdP3F9IAqpU

By: Krysta Del Rosario :)

Empirical Formula

·         Are the simplest formula of a compound

<!--[if !supportLists]-->·         <!--[endif]-->Show only the simplest ratios, not the actual atoms

<!--[if !supportLists]-->-          <!--[endif]-->The empirical formula for Chlorine gas is Cl

<!--[if !supportLists]-->-          <!--[endif]-->Dinitrogen tetraoxide empirical formula is NO2

<!--[if !supportLists]-->·         <!--[endif]-->Molecular formulas give the actual number of atoms

Example:

Molecular Formula	Empirical Formula
P4O10	P2O5
C10H22	C5H11
C6H18O3	C2H6O
C5H12O	C5H12O
N2O4	NO2

 

Atom	Mass	Molar Mass	Moles (mass/molar mass)	Smallest Moles (moles/smallest moles)	Ratio
C	0.576	12.0	0.048	0.048/0.012=4	4
H	0.120	1.0	0.120	0.120/0.012=10	10
O	0.192	16.0	0.012	0.012/0.012= 1	1

http://www.youtube.com/watch?v=gfBcM3uvWfs

By: Krysta Del Rosario :)

Multistep Conversion

12.5 grams of Hydrogen (H2) are placed in a balloon at STP (Standard Temperature and Pressure = 0º C & 101.3 kPa). Determine it's volume.

1. First, use molar mass as your conversion factor and cancel accordingly.

-> 12.5 g of H2 x 1 mol
2.0 g*


*The mass in grams is 2.0 because there are hydrogen is diatomic.

2. Next, use molar volume as your conversion factor and cancel accordingly.

-> 12.5 g of H2 x 1 molx 22.4 L
2.0 g 1 mol

3. Alter your answer to have the appropriate number of significant digits.

-> There are 1.4 x 10² Liters in 12.5 grams of Hydrogen.

http://www.youtube.com/watch?v=_KD0Qc7Jf5k&feature=related

-Candace Chan

Percent Composition

You can find the percentage of the chemical equation by:

1) Adding up the total of the molar mass
2) Divde each element's molar mass to the total molar mass
3) There is the percentage of the element

Example:

C8H18 = 114

C8 = 96 / 114 = 84%
H18= 18 / 114 = 16%
http://www.youtube.com/watch?v=xbEeyT8nK84

-Candace Chan

Density and Moles

Density:

- is a measure of mass per volume.
- is measured in g/mL or g/L
- Formula for density is
         

Example:

Oxygen has a density of 1.0 g/ml. Determine the mass of 11.5 mL of oxygen gas.

11.5 mL x 1.0 g      = 11.5 g
                  1 mL

How many moles are there in 11.5 mL of oxygen?

11.5 g x 1 mol   =  0.639 mol
                18 g


http://www.youtube.com/watch?v=REtBibhIqfo


Density of gases:

The density of gases can vary with the temperture.
If the temperature is at STP, we can find density by "

Molar Mass
22.4 L/mol

Example:

32g/mol       = 1.4 g/ L
22.4L/mol

-Candace Chan