Calculations+involving+the+Mole+and+the+Mass+of+a+Substance+and+the+Volume+of+a+gas

=Calculations involving the Mole and the Mass of a Substance and the Volume of a gas=
 * P81-82**

Note: the unit symbol for "mole" is "mol".
 * For example:** five moles=5 mol

Under no circumstances must you use any other unit symbol for the unit"mole", because all other abbreviations already have their special meanings in chemistry, use other unit symbol will make you feel confuse later on in this course.

**Molar Mass**
In chemistry, the conversion factor is **molar mass** (the mass of one mole). This value has been calculated for each element and is usually included in a periodic table. In most periodic tables of the elements, the molar mass value is located in the top right hand corner of an element's cell.

The following conversion factors are used to relate the number of moles to the mass of matetial present.

produces the conversion factors
 * 1 mol of Y has a mass of (molar mass of X) g

__1 mol__ or __(molar mass of Y)g__ (molar mass of Y)g 1 mol ||
 * Example: 1.What is the mass of 3.25mol of CO2?**

molar mass of CO2=44.0g=mass of 1 mol of CO2 mass of CO=3.25mol x 44.0g/1mol =143g


 * 2. How many moles of N2 are there in 50.0g of N2?**

molar mass if N2=28.0g=mass of 1 mol of N2 number of moles=50.0g x 1mol/28.0g=1.79mol

The units of molar mass are actually **g/mol.** This suggests that the molar mass can be calculated by dividing the mass of a substance by the number of moles contained in the substance.

If 0.140 mol of acethlene gas has a mass of 3.64g, what is the molar mass of acetylene?
 * Practice:**

molar mass=3.64g/0.140mol =26.0g/mol

Avogadro's Hypothesis simplify the calculations involving gas volumes
 * Avogador's Hypothesis:** **Equal volumes of different gases, at hte same te,perature and pressure, cantain the same number of particles.(STP)**

Standard Temperature and Pressure (STP)=<span style="-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; border-collapse: separate; color: #000000; font: medium arial; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; webkitborderhorizontalspacing: 0px; webkitborderverticalspacing: 0px; webkittextdecorationsineffect: none; webkittextsizeadjust: auto; webkittextstrokewidth: 0px; white-space: normal; widows: 2; word-spacing: 0px;">0 °C and 101.3 kPa**
 * Molar Volume:** the volume occupied by one mole of the gas**.

1 mol of ANY GAS at STP has a volume of 22.4L ​(ONLY for gas at STP)
number of litres=0.350mol x 22.4L/mol=7.84L
 * Example: 1.What is the volume occupied by 0.350mol of SO2(g) at STP?

2. How many moles of gas are contained in a balloon with a volume of 10.0L at STP? number of mols=10.0L x 1mol/22.4L=0.446mol**