Paper 1 chem

Avogadro constant

the number of atoms, molecules, or ions in a mole of any substance (i.e., 6.02 × 10-23 per mol)

concentration

the amount of a substance dissolved in a given volume of liquid

limiting reactant

the reactant in a chemical reaction that when used up causes the reaction to stop

mole

the amount of substance in the relative atomic or formula mass of a substance in grams

relative atomic mass Ar

the average mass of the atoms of an element compared with carbon-12 (which is given a mass of exactly 12). The average mass must take into account the proportions of the naturally occurring isotopes of the element

relative formula mass Mr

the total of the relative atomic masses, added up in the ratio shown in the chemical formula, of a substance

percentage by mass

Indicates what proportion of the total mass of a compound is accounted for by each element.

= mass of element/mass of compound x100

atomic number

the number of protons in the nucleus of an atom

balanced equation

chemical equation with the same number of atoms of each element on both sides of the equation

Reacting masses

The masses of elements and compounds which take part in a chemical reaction.

product

A substance produced in a chemical reaction

Coefficient

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

Reactant

A chemical substance that is present at the start of a chemical reaction

ratio

A comparison of two quantities by division

conservation of mass

the principle stating that matter is not created or destroyed during a chemical reaction

yield

to produce

Percentage yield

actual yield/theoretical yield x 100

theoretical yield

the maximum amount of product that can be produced from a given amount of reactant

actual yield

the measured amount of a product obtained from a reaction

Atom economy

(Molecular mass of desired products/ Molecular mass of all products) x 100

Solution

A mixture that forms when one substance dissolves another.

Solute

A substance that is dissolved in a solution.

g/dm3

mass of solute dissolved per dm3

end point

the point in a titration at which an indicator changes color

Burette

a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in titrations.

Pipette

A glass or transparent plastic tube used to accurately measure small amounts of liquid

molar volume of a gas

22.4 L/mol at Standard temperature and pressure

exothermic reactions

reactions that release energy (heat)

endothermic reactions

reactions that absorb energy (heat)

Examples of exothermic reactions

Combustion / neutralisation / oxidation

Examples of endothermic changes

decomposition / photosynthesis / eating sherbet

RP : investigating temp changes

record initial temp of solution / mix reactants in polystyrene cup / use thermometer to measure change

Exothermic reaction graph

reactants higher than products

endothermic reaction graph

reactants lower than products

Hand warmers and self heating cans - exo

Crystallisation of supersaturated solution - reusable hw

oxidation of iron with salt - disposable hw

Instant cold packs - endo

ammonium nitrate and liquid water are mixed / used for sporting injuries / last 20m

Bond breaking

endothermic (needs energy)

Bond making

exothermic ( releases energy )

How to calculate bond energies

- Add together all bond energies for reactants (Energy In)

- Add together all bond energies for products (Energy Out)

- Calculate with Energy In - Energy Out

spectator ions

ions that do not participate in a reaction

Electrical cells

two metals are dipped in a wire and salt solution / more reactive metal will donate its electrons to less reactive metal

The greater reactivity in metals used

The higher the voltage made

hydrogen fuel cell

generates electricity by reacting hydrogen with oxygen

how does a hydrogen fuel cell work

hydrogen reacts with oxygen / h2 goes to anode, looses electron to be H+ ion / crosses a partially permeable membrane/ reacts with 02 and DL electrons to make h20 and electricity

Positive half equation

Element ~> electrons + ion

negative half equations

ion + electrons ~> balanced element

advantages of hydrogen fuel cells

less refuel time / travels further before RF / no loss of efficiency / no pollutants / h2 is abundant

What is electrolysis

the breakdown of a substance containing ions by electricity

Why can ionic compounds only conduct electricity when molten or dissolved

Ions are free to move and carry charges

What happens during electrolysis

Positive ions move to the negative electrode / negative ions move to the positive electrode

What is an electrolyte?

A molten or dissolved ionic compound

What are electrodes

Made of unreactive substances so it doesn't disrupt reactions (graphite)

can also conduct electricity

What happens to ions in electrolysis

When is electrolysis done

To separate ionic metal compound that can't be split using carbon displacement

What do negatively charged ions do

Loose electrons

What do positively charged ions do

Gain electrons

What is reduction

gain of electrons, loss of oxygen ( @ the cathode )

What is oxidation

loss of electrons ( @ the anode )

What happens at the anode if the electrolyte is aqueous

02 gas from dish charged hydroxide ions made from water / halogen if the electrolyte is made of one

Anode

Positive electrode

Cathode

Negative electrode

What happens at the cathode in electrolysis of an aqueous solution

The less reactive element, either the hydrogen or metal is made

What is an aqueous solution?

a solution where water is the solvent

Why do graphite (carbon) anodes have to be replaced often

Slowly burn away as carbon reacts with 02 to make c02 gas

Electrolysis of aluminium oxide

melted with cryolite to lower melting point / aluminium at cathode / oxygen at the anode

What is an ore

rock containing metal compounds

Electrolysis of sodium chloride (brine)

Chlorine gas at the anode / hydrogen gas at cathode / sodium hydroxide solution

use of chlorine

disinfectant in swimming pools

Use of hydrogen

Rocket fuel

Use of sodium hydroxide

soap and bleach

Test for chlorine gas

Bleaches damp litmus paper white

Test for hydrogen gas

Lighted splint. Squeaky pop.

Why can't electrodes touch

Causes a short circuit

Properties of giant covalent structures

no specific formula - can be any size / high melting boiling points- strong CV bonds / one large molecule - no intermolecular forces

examples of giant covalent structures

diamond and graphite

What are pure metals?

giant structures with ions in identical layers / strong electrostatic forces between + ions and - delocalised electrons

properties of pure metals

High MB points - strong electrostatic forces / malleable - ions are in layers s they slide over each other

Why are metals good conductors?

because they have delocalised electrons

properties / structure of diamonds

allotrope of carbon / macromolecular, giant covalent structures / every carbon bonds to 4 other carbons / High MB points / no conductivity - no delocalised electrons / rigid arrangement / insoluble

properties / structure of graphite

each carbon atom forms 3 covalent bonds - each has 1 delocalised electron ( can conduct electricity ) / creates hexagonal rings / soft and brittle - weak intermolecular forces between layers / insoluble

what is the structure of a fullerene

Large, almost spherical shape, hexagonal and pentagonal covalently bonded carbon rings.

buckminster fullerene features

C60 / simple molecules because of fixed shape

Buckminsterfullerene uses

catalysts / lubricants /transporting drugs

cylindrical fullerenes features

shape of cylinder / strong / tiny diameter / can be very long

Cylindrical fullerenes uses

electronics / nano tech / strengthening materials

SA : V ratio in nano particles

surface area to volume ratio is very high

how does sa:v ratio affect nano tech

Allows smaller amounts of material to be used / makes them cheaper

Can nano particles change material properties

yes, some materials in nano particle form have different properties

how are nano particles used in catalysts

high surface area speeds up reactions

how are nano particles used in medicine

fullerene particles can be used to target specific areas of the body

how are nano particles used in electronics

carbon nanotubes used for their electrical conductivity

how are nano particles used in cosmetics

can makes substances transparent

how are nano particles used in deodorants

they have anti microbial properties that can kill odourous bacteria

List 5 uses of nano particles

Medicine / electronics / cosmetics / sun cream / deodorants

Define an alloy

mixture of 2+ elements, at least 1 is a metal ( used for construction )