Chemistry: sept 11 Flashcards by Josh de Graaf

How many decimal points should you measure a burette too

2 decimal points

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what is the boiling point of water

100 degrees celsius

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What element has the atomic number 20

Calcium

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Define relative atomic mass

the ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12.

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What term is used to describe an oxide that reacts with acids and alkalis

Amphoteric

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What should a dot and cross diagram have

dots and crosses

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Mole formula

N = m/mr

moles = mass/molecular mass

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what is a spatula used for

Spatulas are used to transport and distribute dry chemical compounds

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describe ionic compounds

It conducts electricity when dissolved in water
It has a high melting point due to strong attractive forces between ions
the ionic bonds are formed between metallic and non metallic elements

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is this statement about oxides correct: Magnesium oxide reacts with nitric acid to make a salt

Yes

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why are mixtures filtered

To remove the excess filtrate

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Properties of ammonia (NH3)

colourless

less dense than air

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uses of caustic soda (sodium hydroxide)

Drain cleaner

Fertiliser

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What is Calcium carbonate used for (CaCO3)

Kitchen benches (when its marble)

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how to make concrete

CaCO3 is broken down to CaO + CO2 which equals Ca(OH)2

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dissolving

The process in which solvent molecules such as water surround solute particles such as ions
(like those in salt) or molecules (like those in sugar)

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Are all nitrates, sodium, potassium and ammonium salts are soluble.

yes

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What chlorides, bromides and iodides are not soluble

Pb2+, Cu+ and Ag+ are not soluble

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how many flourides are soluble

All of them

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What carbonates are soluble

The carbonates of alkali metals are soluble

The rest aren’t

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What sulphates are soluble

Most sulphates are soluble, Ca2+ and Pb2+ are not Ag+

and Ba2+ are slightly soluble.

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how to perform a flame test

Dip a clean flame test loop in concentrated hydrochloric acid.
Hold the flame test loop at the edge of a roaring bunsen burner flame and ensure the flame does not
change colour. If it does dip in acid again and repeat.
Dip the wire in the solid being testing picking up a few crystals and hold it at the edge of the roaring
Bunsen flame and observe the changed colour of the flame, and decide which metal it indicates.
Clean the loop in acid and rinse with water, then repeat steps 1 to 3 with a new sample.

Ion’s reaction in flames

Lithium (Li+) Red flame
Sodium (Na+) Orange/Yellow flame
Potassium (K+) Lilac flame
Copper(II) (Cu2+) Blue/Green flame

Non metal oxides are

acids

Metal oxide + acid =

salt + water

Metal oxides are

bases

What does hydrated mean

it has water in it

Aqueous ammonia is added to a solution of a salt. A white precipitate is formed which dissolves in an excess of aqueous ammonia. Which metal is in the salt?

Zinc

Two aqueous solutions, X and Y, are mixed together. What pair would not give a white precipitate?

Magnesium nitrate and sodium sulphate

Dilute hydrochloric acid was added to a tube containing a unknown powder. There was a vigorous reaction and a gas was produced which turned lime water cloudy. After the reaction stopped, excess aqueous sodium hydroxide was added to the tube and a green gelatinous precipitate was formed. What was the unknown powder.

FeCO3

When aqueous ammonium chloride was heated with aqueous Y, a gas which turned universal indicator paper blue was evolved. Which ion must have been present in Y?

OH-

What is a fuel

something with stored chemical energy

What does exothermic mean

gives out heat

What does delta H =

enthalpy change

What is the symbol for delta

▵

What does EA mean

Activation energy

why do you need activation energy

to make stuff react

What is the unit of Enthalpy change

KJmol-1

Formula for amount of energy

energy (j) = heat capacity x mass x change in temp

The collision theory

If two particles hit each other at high energy in the right orientation you get a reaction

How does temperature affect rate of reaction

High temperature increases frequency and success

How does surface area affect rate of reaction

larger surface area increases frequency of collisions

How does concentration affect rate of reaction

Higher concentration increases frequency of collisions

How does a catalyst affect rate of reaction

Increase a rate of reaction without being consumed, increases the success of collisions

what increases frequency of collisions

Temperature Surface area Concentration Pressure

What increases success of collisions

Temperature | catalyst

How to speed reaction

warming it Increasing pressure (only gas) increasing concentration Using a catalyst

How does change in concentration affect equilibrium

If the concentration of one side of the equation is lowered for some reason, then the equation will shift so more is made to replace that which is lost. If the concentration of one side is increased, then that side will react quickly to get rid of the excess and restore the equilibrium to what it was.

how does change in temperature affect equilibrium

A change in temperature will affect the equilibrium depending on which direction on the equilibrium is more exothermic. Le Chatelier’s principle applies to a change in temperature because the reversible reaction would be exothermic in one direction and endothermic in the other, so an increase in temperature would mean that the endothermic reaction would be favoured and vice versa. If the temperature is raised, the equilibrium would shift so the less exothermic reaction would occur more and so the temperature would try to fall. If the temperature were lowered, then the equilibrium would shift so the more exothermic reaction would occur more and create ore of the substance at that end of the equation.

How does change in pressure affect equilibrium

If the equation is off gasses and has different numbers of molecules on both sides, the equilibrium would shift so the pressure could be restored back to what it was.

How does adding a catalyst affect equilibrium

The addition of a catalyst does not change the concentrations of reactants or products. It does speed up the reaction rate in both forward and reverse directions and allows the system to reach equilibrium more rapidly.

what does homogeneous mean

A substance is homogeneous if its composition is identical wherever you sample it - it has uniform composition and properties throughout.

what does dynamic mean

In chemistry, and in physics, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change.

what does equilibrium mean

Chemical equilibrium, condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs. A reversible chemical reaction is one in which the products, as soon as they are formed, react to produce the original reactants.