# Atoms and reactions

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What does the mass (nucleon) number represent?
total number of protons and neutrons in the nucleus
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What does the atomic number represent?
The number of protons in the nucleus (defining the element)
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What are isotopes?
atoms of the same element with the same number of protons but different numbers of neutrons (different masses.)
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What determines the chemical properties of an element?
The number and arrangement of electrons.
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What do physical properties depend on?
The mass of an atom (neutrons and protons)
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Define relative atomic mass
The weighted mean mass of an atom of an element compared to one twelfth of the mass of an atom of carbon-12.
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Define relative isotopic mass
The mass of an atom of an isotope compared to one twelfth of the mass of an atom of carbon-12
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Define relative molecular mass
The weighted mean mass of a formula unit/molecule compared to one twelfth of the mass of an atom of carbon-12.
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What is a mole?
A large number of particles (6.02 x 10^23- the Avogadro constant.) It's the measurement of the amount of substance
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How do you work out the number of particles you have?
moles x (6.02 x 10^23)
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What is molar mass?
the mass per one mole of something- the same as the relative molecular mass.
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Number of moles= ?
mass in g / molar mass
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1 dm^3 = ? cm^3
1000 cm^3
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How do you calculate the concentration of a solution?
moles / volume in dm^3
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How do you calculate the number of moles of GAS?
volume in dm^3/ 24
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What is the empirical formula?
The smallest/simplest whole number ratio of atoms in a compound
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What is the molecular formula?
The actual numbers of atoms in a molecule
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What do acids and bases do in aqueous solutions?
Acids produce hydrogen ions (proton donors.) Bases remove or take hydrogen ions (proton acceptors.)
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What are the hydrogen ions donated by an acid replaced by?
metal ions or ammonium ions, forming a salt.
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What are examples of common bases?
Metal oxides, metal hydroxides and ammonia.
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What is an alkali and what are common examples of alkalis?
A base that is soluble in water, sodium hydroxide and potassium hydroxide (+ aqueous ammonia)
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What happens to alkalis in water?
They release hydroxide ions which accept hydrogen ions to form water molecules.
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Metal Oxide + Acid --->
salt + water
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Metal Hydroxide + Acid --->
salt + water
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Metal + Acid --->
Metal Salt + Hydrogen
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Metal Carbonate + Acid --->
Metal Salt + Carbon Dioxide + Water
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What is the water in a lattice called?
water of crystallisation
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What is a hydrated salt?
A salt containing water of crystallisation
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What is an anhydrous salt?
A salt not containing water of crystallisation
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What is the colour change of methyl orange when acid is added to an alkali?
Yellow to red
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What is the colour change of phenolphthalein when acid is added to an alkali?
pink to colourless
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What is oxidation and reduction?
oxidation: loss of electrons and increase in oxidation number. Reduction: gain of electrons and decrease in oxidation number.
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What happens to oxidising agents and reducing agents?
oxidising agents are reduced and accept electrons. reducing agents are oxidised and donate electrons.
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which form are oxidation numbers written in?
In Roman numerals
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What are the rules for assigning oxidation numbers?
Uncombined elements=0. Diatomic elements=0. In compound or compound ions, the OVERALL oxidation= charge of ion. sum of neutral compound= 0. combined oxygen= -2. combined hydrogen= +1. Monatomic ion= same as charge.
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Metals generally form ions by...
losing electrons with an increase in oxidation number to form positive ions.
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non-metals generally react by...
gaining electrons with a decrease in oxidation number to form negative ions.
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When a metal reacts with dilute hydrochloric acid or sulfuric acid...
metal atoms are oxidised, losing electrons and forming soluble metal ions. Hydrogen ions in the solution are reduced, forming hydrogen molecules.
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What are the steps for carrying out a titration?
Using a pipette, measured volume of one solution is added to a conical flask. Indicator is added. The other solution is placed in the burette. Solution from the burette is added to the conical flask until a colour change occurs.
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## Other cards in this set

### Card 2

#### Front

What does the atomic number represent?

#### Back

The number of protons in the nucleus (defining the element)

### Card 3

#### Front

What are isotopes?

### Card 4

#### Front

What determines the chemical properties of an element?

### Card 5

#### Front

What do physical properties depend on?