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?
Annotate the first three rows of this table:
Columns = groups --> Number of electrons in the outer shell
Rows = periods --> Number of shells
Number of neutrons: 9, 10, 36
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:
A) H2 + O2 → H2O
B) KClO3 → KCl + O2
A) 2 H2 + O2 → 2 H2O
B) 2 KClO3 → 2 KCl + 3 O2
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
Calculate the molecular mass of the following compounds.
MgO:
FeBr3:
Atomic masses: Mg = 24 ; O = 16; Al = 27; Fe = 56 ; Br = 80
MgO:
24 + 16 = 40 u or amu
FeBr3:
56 + 3x80 = 296 u or amu
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
Balance the following equations:
A) Zn + HCl → ZnCl2 + H2
B) CH4 + Cl2 → CCl4 + HCl
A) Zn + 2HCl → ZnCl2 + H2
B) CH4 + 4 Cl2 → CCl4 + 4 HCl
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 water
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 %
Calculate the molar mass of the following compounds.
Al2S3:
Ca(OH)2:
Atomic masses: Al = 27; S = 32; Ca = 40; H = 1.
Al2S3:
2x27 + 3x32 = 150 g/mol
Ca(OH)2:
40 + 2x(16+1) = 74 g/mol
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
Balance the following chemical reactions:
A) Sodium + O2 → Sodium oxide
B) Sodium chloride + F2 → Sodium fluoride + Cl2
A) 4 Na + O2 → 2 Na2O
B) 2 NaCl + F2 → 2 NaF + Cl2