Ch3: CHEMISTRY FUNDAMENTALS

Question 1

What does a mole measure? What is its abbreviation?

Answer 1

Amount of substance

mol

Question 2

What does an ampere measure? What is its abbreviation?

Answer 2

Electric current

A

Question 3

What are the six SI base units?

Answer 3

Meter (m)
Kilogram (kg)
Second (s)
Mole (mol)
Kelvin (K)
Ampere (A)

Question 4

What do prefix symbols m and M represent ?

Answer 4

Milli and Mega

Question 5

1000L = ___ m³

Answer 5

1

Question 6

1L = ___cm³

Answer 6

1000

Question 7

1mL = ___ cm³= ___ cc

Answer 7

1 and 1

Question 8

What is an angstrom? what is its abbreviation? What does it measure?

Answer 8

abbreviated Å
Measures length
Unit of length equal to 10^ -10m

Question 9

What is an order of magnitude?

Answer 9

An order of magnitude is an approximation of of the logarithm of a value relative to some contextually understood reference value.

Often is the power of 10 a number is raised to when its in scientific notation

for ex. the order of magnitude for 19, 400 would be 4

Question 10

Density equation

Answer 10

Density= Mass/ Volume

Question 11

What are the units of density?

Answer 11

Most often kg/m³
In chemistry its more often g/cm³

Question 12

kg/m³ —–> g/cm³

Answer 12

divide by 1000

Question 13

g/cm³ —–> kg/m³

Answer 13

Multiply by 1000

Question 14

Define molecule

Answer 14

When two or more atoms form a covalen bond

Question 15

Molecular formula

Answer 15

A compounds molecular formula gives the identities and numbers of the atoms in the molecule

Question 16

Empirical Formula

Answer 16

A formula for a compound in which the number of atoms in each element in the compound are represented by the lowest whole number ratio

Question 17

What is the empirical formula for C2H6O2?

Answer 17

CH3O

Question 18

Formula/ molecular weight. Whats the difference.

Answer 18

Formula weight: Sum of atomic weights of all the atoms in the molecule

Molecular weight typically used when a compound exists as discrete molecules

Question 19

Atomic mass unit

Answer 19

amu
Is the atomic mass that is listed for each element on the periodic table

Question 20

What is a mole? What is the number that represents a mole?

Answer 20

A particular number of things

mole= 6.02 x 10²³ entities

This is avogadros number

Question 21

If an atom of sodium has a mass of 23 amu, 1 mole of sodium atoms has a mass of ___g

Answer 21

23

Question 22

Whats the formula/ what are the steps for calculating the percentage composition by mass in a compound?

Answer 22

Calculate the total molecular weight of the compound

Calculate the weight of each element to see their contribution to the total mass in g

% of the element= Mass of the element / Total mass of compound

Question 23

Which contains more formula units; a 1-mole sample of potassium dichromate or a 1 mole sample of lead azide?

Answer 23

Trick question, both samples contain the same number of formula units, namely 1 mole of them

Question 24

How would you mathematically approach this question?

What is the empirical formula of a compound that is, by mass, 90% Carbon and 10% Hydrogen?

Answer 24

Assume the compound is 100g. 90g carbon, 10g hydrogen

Calculate the number of moles of Carbon if there are 90g of Carbon, and 1 mole of Carbon is 12 g/mol.
#moles of C: 90g / 12g/mol

               #moles of H:    10g      /      1g/mol 

Perform ratio of amount of C to amount of H

15/2 / 10 = 15/20 = 3/4

Thus C3H4

Question 25

What is Molarity (M)?

Whats the formula?

Answer 25

The concentration of a solution in terms of moles of solute per volume (in Litres) of solution

Molarity (M)= #moles of substance S / total # moles in
solution

Question 26

What is mole fraction?

Formula?

Answer 26

The fraction of moles of a given substance (S). So finding it for just one element in a compound

Mole Fraction of S = Xs = #moles of substance S
———————————–
total # moles in a solution

Question 27

Law of conservation of Mass (Matter)

Answer 27

The amount of matter (and thus mass) does not change in a chemical reaction

Demonstrated by balanced equations: for every element represented the number of atoms on the left side of the arrow is equal to the number of atoms on the right side

Question 28

Stoichiometric coefficients

Answer 28

Coefficients preceding each compound depicting in what proportion the reactants react and in what proportion the products are formed