Agriculture Chemistry Chapter 10

Measuring Matter 3 ways to measure matter –By count 1 dozen apples –By mass2.0 kg apples –By volume.20 bushels apples 1 dozen apples2.0kg apples1 dozen apples 12 apples1 dozen apples.20 bushel apples What is the mass of 90 average-sized apples if 1 dozen of the apples has the mass of 2.0kg?

Dimensional Analysis If.20 bushel is 1 dozen apples and a dozen apples has the mass of 2.0kg, what is the mass of.50 bushel of apples?

Dimensional Analysis Assume 2.0 kg of apples is 1 dozen and that each apple has 8 seeds. How many apple seeds are in 14 kg of apples?

What is a Mole? To count representative particles in chemistry, we use the mole (mol). –Representative particles = atoms, molecules, or formula units. 1 mol = 6.02 x 10^23 Called Avagadro’s number = famous dead guy A mole of ANY substance is 6.02 x 10^23 representative particles 1 mol6.02 x 10^23 representative particles 6.02 x 10^23representative particle 1 mol

Question!!! How many representative particles are in… A. a mole of water? B. a mole of Calcium? C. a mole of sugar? D. a mole of eggs? E. a mole of Copper(II) Sulfate?

How large is a mole? 1 mole of marshmallows= 18 miles high, covering Earth’s surface 1 mole of dollar bills to the moon and back 80 billion times

The mass of a mole of an element 1 mole = # C atoms in 12g Carbon (6.02 x 10^23) Atomic Mass in grams = mass of 1 mole (6.02 x 10^23 atoms) of the element. – Called Molar Mass, measured in grams per mole (g/mol). The Molar Mass of any two elements must contain the same # atoms. – 12.0g Carbon and 16.0g Oxygen have same # atoms. (they just weigh different) Question: How many atoms are contained in the molar mass of any element?

What’s the molar mass of… Nitrogen Phosphorus Potassium

Let’s try one! Iron is a common metal used in making agricultural implements. How many moles of Iron is 1.25 x 10^23 atoms of Iron? Steps to Success 1 st List Knowns and Unknowns 2 nd Always write what you’re given 1 st 3 rd Set up units so they cancel out and the end unit is on the top right 4 th Do arithmetic

You try!!! How many moles is 2.80 x 10^24 atoms of silicon? How many moles is 2.17 x 10^23 representative particles of bromine?

Converting Moles to Number of Atoms Suppose you own a dairy and are curious about the methane emissions from your cows. You want to know how many atoms are in 2.12 mol of methane (CH 4 ). Knowns: -Number of moles = 2.12 mol CH4 -1 mol CH4 = 6.02 x 10^23 molecules CH4 -1 molecule CH4 = 5 atoms (1 carbon and 4 hydrogen) -Desired conversion is: moles > molecules > atoms Unknowns: -# atoms? Solve:

You Try How many atoms are in 1.14 mol SO 3 ? Sulfites are used in wine making and preserving fruit!

The mass of a mole of a compound Add atomic masses of atoms that make up a compound or molecule. Find Molar Mass of: H 2 0 C 6 H 12 O 6 CH 4

You Try It! 1. Find the molar mass of PCl 3 2. What is the mass of 1.00 mol of sodium hydrogen carbonate?

Molar Mass Madness! Travel to each station and answer each problem Write down question and answer on piece of paper

10.2 Mole-Mass and Mole-Volume Relationships

The Mole-Mass Relationship Use molar mass of an element or compound to convert between the mass of a substance and the moles of a substance. Example: Let’s say you need 3.00 mol of salt (NaCl) for a recipe. How do you measure this amount? 1 st Find Molar mass of NaCl = 58g 2 nd Multiply by a conversion factor

Practice! Rust is often a problem in agriculture because it weakens chains or other machinery made of iron. When iron is exposed to air, it corrodes to form red-brown rust. Rust is iron(III) oxide (Fe 2 O 3 ). How many moles of iron(III) oxide are contained in 92.2 g of pure Fe 2 O 3 ? KnownsUnknowns -Mass 1 mol Fe2O3=# moles?

Try on your own Elemental Boron is needed in alfalfa plants to prevent stunted growth. In corn, a boron deficiency results in twisted ears and barren stocks. Find the # moles in 3.70 x 10^-1 g of boron.

Mole-Volume Relationship Avagadro’s Hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of particles. –Particles of different gases are not the same size. –BUT particles in all gases are so far apart that larger particles don’t need much more space than the same # or smaller particles. –Insert Picture Here –Balloons in room blown up to diff sizes

Standard temperature and pressure (STP):