Chemical Reactions Flashcards
What is a salt?
A product formed when an acid reacts with a metal, base or carbonate and comprises of a metal and a non-metal.
acid + base
salt + water
acid + metal
salt + hydrogen gas
acid + oxygen
metal oxide
acid + metal carbonate
salt + water + carbon dioxide
What is pH?
The pH scale is a measure of the concentration of hydrogen ions in a solution.
Ocean Acidification
Absorption of excess carbon dioxide then the dissolved CO2 forms carbonic acid, which leads to a lowering of the pH of the oceans as they have become more acidic. This impacts marine life, inhibits the ability of organisms such as corals and shellfish to form protective structures.
Acid Rain
Acid rain is formed when pollutants, particularly sulfur
dioxide (SO2) and nitrogen oxides (NOx), emitted from human activities like burning fossil fuels, interact with water vapor in the atmosphere. These gases form sulfuric acid and nitric acid, leading to precipitation with lowered pH levels, causing
environmental damage to soil, water bodies, and vegetation. These strong acids also corrode the upper layers of buildings and monuments that are made up of marbles and damages them. This can reaction is the acid + carbonate = salt + water + carbon dioxide reaction.
Generalised word equation for combustion
hydrocarbon + oxygen = carbon dioxide + water
A chemical equation shows…
All the atoms involved in the reaction and how they rearrange into the products.
What are indicators (universal and natural)
An indicator is a substance that changes colour in the presence of an acid or a base. In a laboratory, a universal indicator can be used to test the strength of the acidic or basic solution that is being tested. Other natural indicators such as beetroot or cabbage can be used to determine whether a substance is an acid or a base However, these indicators are not as accurate as universal indicator.
Closed system
Closed system: is one in
which nothing can
escape.
Open system
Open system: is when
reactions that produce
gases will appear to lose
or gain mass.
Acid characteristics
*All contain at least one Hydrogen ion
● Have a sour taste
● Conduct electricity when mixed with water
● Can neutralise bases
● React with many metals
● Have a pH less than 7 (red or orange)
● Common examples include: Oranges, lemons, grapes, apples, vitamin c, yoghurt, vinegar, soft drink
● Chemical examples include:
Hydrochloric acid HCl, Nitric acid HNO3 and Sulfuric acid H2SO4
* Sting and burn skin
Base characteristics
● Bases that dissolve in water are called alkalis
● Have a bitter taste
● Have a soapy/slippery feel to them
● Have a pH greater than 7 (blue and green)
● Common examples include: many
household cleaners (good at
dissolving grease).
● Chemical examples include: Sodium
Hydroxide NaOH, Potassium
Hydroxide KOH and Barium Hydroxide
Weak and strong acids
WEAK ACIDS
● Do not easily give away Hydrogen
ions
● Much safer than strong acids
● We eat and drink many weak acids
● Weak acids are used as
preservatives in food
STRONG ACIDS
● Readily give away their Hydrogen
ions
● They are corrosive i.e. will burn
through objects
Strong acids have a low pH eg. 0-2, weak acids have a higher pH eg. 5-6. Strong acids produce a high concentration of hydrogen ions in solution weak acids produce a low concentration.
Weak and strong bases
WEAK BASES
● Generally the bases found in
household cleaning products because
they are safer than strong bases
STRONG BASES
● Attack living tissues and cause serious
burns
● Are caustic and very harmful
Strong bases have a high pH. Concentrated bases have a large number of base molecules in a given volume of water.
What is a chemical reaction?
When the atoms in the existing substances are rearranged to make new substances.
.
Energy changes in reactions
Spontaneous reactions do not require any energy input to get started.
Non-spontaneous reactions require
an energy input.
This energy input is
called the activation energy.
Exothermic reactions
Reactions which release heat or light energy. The reactants have a lot of energy stored in the bonds between the atoms. When these bonds break, energy is
released.
Eg. Combustion
(burning something)
heat is released e.g.
a match
Respiration, heat
packs, acid/base
reactions, Calcium
Chloride (CaCl2)
reacting with water.
Endothermic reactions
Reactions which absorb
energy from its surrounds.
There is not enough
energy in the reactants for
the reaction to ‘go ahead’
so extra energy is taken
from its surrounds. eg.
Thermal or light energy.
Eg. Photosynthesis, light
energy is absorbed
Potassium Nitrate
(KNO 3) reacting with
water.
What test to discover certain gasses?
Test
Observation
Inference
Glowing splint held in a test tube Splint relights
Oxygen is present
Lighted splint held in a test tube Pop sound heard
Hydrogen is present
Gas bubbled through limewater Limewater turns milky or cloudy white
Carbon dioxide is present
Damp litmus paper held in a test tube
Paper turns white
Chlorine is present
What is the pH levels for bleach, lemon juice, ammonia, baking soda, vinegar, tomato juice, water
Bleach: 11-13
Lemon Juice: 2-3
Baking soda: 9
Ammonia: 11-13
Vinegar: 2-3
Tomato Juice: 4.1
Water: 7
