Thursday, November 18

This morning, we walked into class and were notified that there was a lab today. The lab is called ST1 Copper and Silver Nitrate Lab. The purpose is to use careful measurements to determine the mole ratio of copper(II) and silver in the single replacement reaction of silver nitrate with copper. We were instructed to take out our lab notebooks and copy down this purpose onto a clean right-side page. On the left side, Mr. H told us to write the chemical equation for the reaction, for it would be helpful later. It is:

Cu (s) + 2AgNO3 (aq) --> 2 Ag (s) + Cu(NO3)2 (aq)

We all then received a piece of paper describing the lab's procedure. 2 people from the lab group were to carry out the first procedure while the remaining 2 were to carry out the second procedure. The procedures are as followed:

1) Prepare the Silver Nitrate for Reaction:

• Mass an empty 50 mL beaker. Record.
• Add ~1.4-1.6 g of AgNO3.
• Mass beaker plus AgNO3. Record.
• Add 30 mL of water.
• Stir to dissolve solid; rinse stirring rod so as to avoid loss of the AgNO3.

2) Prepare Copper for Reaction and React:

• Obtain ~25 cm of copper wire.
  
• Mass wire. Record.
  
• Loosely coil the wire so as to rest of a wood splint as shown. It should be long enough to hang on the wood splint and dangle in the solution. Yet it should not touch the bottom of the beaker.
  
• Add 3 drops of nitric acid to the solution; avoid contacting the copper wire with the HNO3. Do not stir.

After we did what was required, we were instructed to leave our notebooks at our lab benches and come back to our seats. This time was set aside for the reaction to occur. When we were back at our desks, Mr. H told us to take out our packets and turn to page 6 for

E V E N M O R E S t o i C H E o M I S T R Y!!!!

Mr. H told us to do number 7; write the balanced equation for the synthesis of magnesium oxide from its two elements - magnesium and oxygen. The answer is as follows:

2Mg (s) + O2 (g) = 2 MgO (s)

Then we were told to do number 8; calculate the molar mass of each of the three reactants and products. The answer is as follows:

Mg: 24.305 g/mol O2: 32.0 g/mol MgO: 40.3 g/mol

After, as a class, we went through the next three problems and identified how many steps would be needed (using the Mole Island method, of course). Number 9 was a one step equation. Number 10 was a two step equation. And number 11 was a three step equation.

The answer to number 9 (Determine the number of moles of magnesium oxide produced by the reaction of 3.25 moles of magnesium.) is 3.25 molecules of MgO, simply found by using Mole Island to convert from moles of magnesium to moles of magnesium oxide.

The answer to number 10 (Determine the mass of magnesium oxide produced by the reaction of 5.22 moles of magnesium.) is 210.39 g MgO, again, simply found by using Mole Island to convert from moles of magnesium to moles of magnesium oxide to grams of magnesium oxide.

The answer to number 11 (Determine the mass of oxygen gas which will react with 65.2 grams of magnesium.) is 42. 92 g O2, aaaaaaand again, simply found by using Mole Island to convert from grams of magnesium to moles of magnesium to moles of oxygen to grams of oxygen.

Before we knew it, it was time to check back at our lab. Our whole lab group was to do the third and fourth procedures listed on the sheet of paper:

3) Retrieve Silver Product from Copper Wire:

• Obtain a clean, dry 100 mL beaker. Using a permanent marker, label it with your period and your names.
• Mass the empty beaker. Record.
• Carefully lift the copper wire (with silver attached) from the beaker.
• Hold wire over and into 100 mL beaker and rinse with a forceful stream of DI water. The goal is to knock the silver off the copper and into the beaker.
• Continue rinsing until all the silver crystals are removed.
• Set labeled beaker aside to dry. Once dry (the next class period), mass the beaker with the silver. Record.

4) Rinse and Mass Unreacted Copper:

• Rinse the remains of the copper wire in an acetone bath.
• Being careful not to break or crumble the copper, thoroughly dry it by dabbing it with a paper towel.
• Mass the remaining copper wire. Record.

We did just that. The untouched product (silver still connected in the original beaker) should look like this:The removal of the silver should look like this:

Mr. H then told us to clean up and reminded us that we would be finishing the lab tomorrow.

The homework is the Stoich WebAssign 2.