Pre-Lab Questions Write your answers in pen and include units. 1. Write out the

Question

Pre-Lab Questions Write your answers in pen and include units. 1. Write out the number of items in a mole in a. scientific notation: b. standard notation: 2. The number of items (atoms) in a mole is named for a famous chemist. By what name do we know this number? 3. One mole of ethanol molecule, C2H,O, contains a. how many carbon atoms? b. how many hydrogen atoms? c. how many oxygen atoms? 4. Define the following terms: a. limiting reactant (or limiting reagent) - b. theoretical yield - percent yield- 81

Explanation / Answer

We know 1 mol of substance contains 6.02E23 entities

For example 1 mol C atom = 6.023 E23 atoms

Answer : 1). A . scientific notation :

6.02 X 1023 items

b) Standard form:

602214150000000000000000.

2).

The name of the Scientist : Amedeo Avogadro

The number is called as Avogadro’s number.

3).

1 mol Ethanol contains:

a). Carbon atom :

1 mol ethanol contains 6.02E23 ethanol molecules

1 molecule of ethanol contains 2 Carbon atoms.

Lets use these two relation to get number of carbon atoms.

Number of C atoms in 1 mol ethanol

= 1 mol ethanol *(6.02E23 ethanol molecules /1 mol ethanol molecules )*(2 C atoms /1 ethanol molecule) =1.204E24 C atoms

Number of H atom

=1 mol ethanol *(6.02E23 ethanol molecules /1 mol ethanol molecules )*(6 H atom /1 ethanol molecule)

= 3.61E24 H atoms

Oxygen atom:

= 1 mol ethanol *(6.02E23 ethanol molecules /1 mol ethanol molecules )*(1 O /1 ethanol molecule)

= 6.02E23 O atoms.

Q. 4 )

The reactant which limits the product formation in the reaction is called as limiting reactant.

Its amount in the reaction is less than that of the stoichiometric limit.

For example

N2 + 3 H2 --- > 2 NH3

In above reaction there requires 3 mol of H2 for 1 mol N2

If 1 mol of N2 reacts with 2 mol of H2 then H2 becomes limiting reactant since its amount is less than the stoichiometric need.

b.

Maximum amount of the product that is formed in the reaction that is calculated by using the moles of the limiting reactant.

c.

Percent yield :

When we get actual yield in the reaction that may be less that of the theoretical yield. We calculate percent yield by using following formula.

Percent yield = Actual yield / theoretical yield * 100 %

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