Physical quantities, scientific notation & conversion factors
Unit and symbol name of "Amount of substance".
unit name: mole, symbol name: mol
Definition of mass and volume.
Mass is the amount of matter in an object.
The volume is the space an object occupies.
A) Chlorine has 18 neutrons and Z = 17. How many electrons does it have and what is its mass number?
B) How many electrons, protons, and neutrons would a chlorine isotope have if A = 37?
A) Z=17 means it has 17 protons. If we have a neutral atom, the number of protons is the same as the number of electrons so it has 17 electrons.
A = Z+ N = 17 + 18 ; A = 35
B) Number of protons and electrons does not change, so 17 protons and 17 electrons.
A = Z + N, therefore:
37 = 17 + N
N = 37 – 17 = 20, so the element has 20 neutrons.
Write the oxidation numbers of the following elements:
Oxygen, Chlorine, Zinc, Gold, Iron.
Oxygen: -2
Chlorine: +/-1, +3, +5, +7
Zinc: +2
Gold: +1, +3
Iron: +2,+3
Complete the following sentence:
In a chemical reaction, the starting materials are the _________ and the new substances formed are the _________. A chemical reaction involves a change in the ___________ forming the initial substances, to give different ones.
In a chemical reaction, the starting materials are the reactants and the new substances formed are the products. A chemical reaction involves a change in the chemical bonds forming the initial substances, to give different ones.
Definition of a derived physical quantity, give also an example
A derived physical quantity is a combination of base physical quantities. E.g speed, density...
What is density? What is the SI unit of density?
Density is the relation between the mass and the volume of an object: m/v .
The SI unit of density is kg/m3 .
What are the columns and the rows in the periodic table? what do you learn from them?
Explain where metal and non-metal elements are located, and if they tend to form cations or anions.
Columns = groups --> Number of electrons in the outer shell
Rows = periods --> Number of shells
Metals are at the left part and in the middle, they tend to form cations. Non-metals are on the top-right, they tend to form anions.
Name the following ions:
Fe3+
S2-
Al3+
Fe3+: Iron (III) cation
S2-: Sulfide anion
Al3+: Aluminium cation
Explain the law of conservation of mass.
The law of conservation of mass states that in a chemical reaction mass is conserved. Matter is not destroyed nor created, it is transformed, there is a change.
That is to say that the total mass of the reactants equals the total mass of the products
or
that the number of atoms at the beginning and the end has to be the same.
Scientific notation of 7,350.
7.35 x 103
Calculate the volume in ml of an iron nail with a mass of 20 g, if the density of iron is 7.9 g/cm3.
Data: m = 20 g ; ρ = 7.9 g/cm3
Formula: ρ = m/v
Calculations: v = m /ρ = 20 / 7.9 = 2.53 cm3 = 2.53 mL Remember: 1 cm3 = 1 mL
The following information is for a Carbon atom: Z = 6 and A= 12. Draw the electronic configuration of this element.
Formulate the following compounds:
Aluminum oxide
Nitrogen(V) oxide
Copper(I) oxide
Aluminum oxide: Al2O3
Nitrogen(V) oxide: N2O5
Copper(I) oxide: Cu2O
Balance the following equations:
Zn + HCl → ZnCl2 + H2
KClO3 → KCl + O2
Zn + 2HCl → ZnCl2 + H2
2KClO3 → 2KCl + 3O2
Scientific notation of 0.06457.
6.457 x 10-2
How many grams of solute do I need to make 400 cm3 of a solution with a mass concentration of 12g/L?
Data:
Volume of solution = 400 cm3 = 400 ml = 0.4 L Mass concentration = 12 g / L
Formula:
Mass concentration = mass solute (g) / volume solution (L)
Calculations:
12 g /L = mass solute (g) / 0.4 L
mass of solute (g) = 12 g/L x 0.4 L = 4.8 g
How much Lithium (mass) do I have if I know the sample contains 15 moles?
RAM = 6.941 g/mol
Data:
RAM of Li = 6.941 g/mol
Mass of Li?
n of Li = 15 mol
Formula:
n (mol) = mass (g)/RAM (g/mol)
mass (g) = n (mol) x RAM (g/mol)
Calculations:
mass = 15 x 6.941 = 104.115 g
Name the following compounds:
Cu(OH)2
Au(OH)3
Al(OH)3
Cu(OH)2: Copper(II) hydroxide
Au(OH)3: Gold (III) hydroxide
Al(OH)3: Aluminium hydroxide
What are the 5 main factors that affect the reaction rate? Explain them.
Concentration: more concentration, more collisions, more reaction.
Temperature: more temperature, higher kinetic energy, more collisions, more reaction
Pressure: more pressure, less space, more collisions, more reaction.
Surface area: more surface area, greater the chance of particles colliding with each other, more reaction.
Catalyst: the collisions between molecules will need less energy, more reaction.
Use conversion factors to transform 110 km/h into m/s.
30.56 m/s
We dissolve 20 g of NaCl in 100 mL of pure water. Calculate the concentration of the solution in mass %.
Data:
ρ = 1 g/ml pure wate
Mass of pure water = 100 ml x 1g/1ml = 100 g
Mass of solute = 20 g
Mass of solution = 100 g + 20 g = 120 g
Formula:
Mass % = (mass solute / mass solution) x 100
Calculations:
Mass % = (20 g / 120 g) x 100 = 16.67 %
How many grams are in 18.022 x 1023 particles of NaCl?
Atomic masses: Na:23; Cl:35.5
Data:
RAM NaCl = 23 + 35.5 = 58.5 g/mol
1 mol = 6.022 x 1023 particles
Since we have 18.022 x 1023 particles…
18.022 x 1023 x 1mol / 6.022 x 1023 = 3 mol
Formula:
n (mol) = mass (g)/RAM (g/mol)
mass (g) = n (mol) x RAM (g/mol)
Calculations:
mass (g) = 3 x 58.5 = 175.5 g
Name or formulate the following compounds:
Cu2S
Boron chloride
PbI4
Copper(I) Iodide
Cu2S: Copper(I) sulfide
Boron chloride: BCl3
PbI4: Lead (IV) iodide
Copper(I) Iodide: CuI
Given the following chemical reaction:
4 Na + O2 → 2Na2O
Atomic masses: Na: 23; O:16
A) How many moles of sodium oxide are produced?
B) How many grams of sodium are consumed?
A) How many moles of sodium oxide are produced?
2 moles of Na2O are produced
B) How many grams of sodium are consumed?
4 mol x (23 g)/(1 mol) = 92 g of Na are consumed