OCR A GCSE Chemistry: Predicting, Monitoring, and Global Challenges

Flashcards covering predicting reactions, identifying products, group trends, transition metals, rates of reaction, equilibrium, and industrial chemistry processes based on OCR A GCSE Chemistry Topic 4, 5, and 6 notes.

How do Group 1 metals react when placed in water?

They react vigorously to create an alkaline solution and hydrogen.

What is the trend in boiling points for Group 0 elements as you go down the group?

The boiling points of the noble gases increase with increasing relative atomic mass.

Using LaTeX, what is the charge of a halide ion in an ionic compound formed with a metal?

$$-1$$

Why do the halogens become less reactive as the energy level of the outer electrons increases?

Electrons are less easily gained because they are less strongly attracted to the positive nucleus.

How do transition metals compare to Group 1 metals in terms of physical properties?

Transition metals are harder, stronger, have higher melting points (except mercury), and have higher densities.

What is the chemical test for Carbon dioxide?

Bubble the gas through limewater (carbon hydroxide) and it will turn milky or cloudy.

What is the observed result when a damp litmus paper is put into Chlorine gas?

The litmus paper is bleached and turns white.

Describe the positive result for a Hydrogen gas test.

A burning splint held at the open end of a test tube creates a ‘squeaky pop’ sound.

When testing aqueous cations with sodium hydroxide ($NaOH$), which ion forms a blue precipitate?

Copper (II)

What distinguishes the reaction of Zinc with sodium hydroxide ($NaOH$) from that of Calcium?

Both form a white precipitate with a few drops, but the Zinc precipitate re-dissolves in excess $NaOH$, while the Calcium precipitate does not change.

What are the precipitate colors for Chloride, Bromide, and Iodide when tested with silver nitrate solution?

Chloride gives a white precipitate, Bromide gives a cream precipitate, and Iodide gives a yellow precipitate.

What color does the flame turn during a flame test for Lithium and Potassium?

Lithium turns the flame crimson, and Potassium turns it lilac.

What equation is used to calculate the moles of a solute in a known volume and concentration?

$$\text{moles} = \text{concentration} \times \text{volume}$$

What is the volume of $1\text{ mol}$ of any gas at RTP (room temperature and pressure)?

$$24\text{ dm}^3$$

How is percentage yield calculated?

$$\text{Percentage yield} = \frac{\text{Amount of product produced}}{\text{Maximum amount of product possible}} \times 100$$

What is the definition of atom economy?

A measure of the amount of reactants that become useful products or the efficiency of a reaction.

How does increasing the temperature affect the rate of reaction in terms of particles?

It increases the speed of moving particles so they collide more frequently and energetically.

How do catalysts increase the rate of reaction?

By providing an alternative pathway with a lower activation energy.

According to Le Chatelier’s Principle, what happens if the concentration of reactants is increased in a system at equilibrium?

The position of equilibrium shifts towards the products (right) until equilibrium is reached again.

In a gaseous reaction at equilibrium, what effect does an increase in pressure have?

It favours the reaction that produces the least number of molecules.

What is Phytoextraction?

A biological method where plants absorb metal compounds through their roots, concentrate them, and are then burned to produce ash containing the metal.

What are the common industrial conditions used for the Haber process?

Purified nitrogen and hydrogen are passed over an iron catalyst at about $450\text{ }^\text{∘}\text{C}$ and $200\text{ atmospheres}$ of pressure.

What is an alloy, and why are metals like Gold usually used as alloys in jewellery?

An alloy is a mixture of metals; pure gold is too soft for everyday use, so it is mixed with silver, copper, and zinc to make it harder.

What is Sacrificial protection in the context of corrosion?

A more reactive metal (e.g., Zinc) is used to galvanise a less reactive metal (e.g., Iron), so the more reactive metal rusts first and protects the layer underneath.

List the first four prefixes for organic compounds and the number of carbons they represent.

Meth- (1), Eth- (2), Prop- (3), and But- (4).

What is the chemical test used to identify a $C=C$ double bond in alkenes?

The addition of bromine water, which changes color from orange to colourless.

What are the four different nucleotides that make up the polymer DNA?

Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).

How does a fractionating column separate the hydrocarbons in crude oil?

It works continuously by piping in heated crude oil; the vaporised oil rises and condenses at different levels where the temperature matches the boiling points of specific fractions.

What are the two common methods for cracking hydrocarbons?

Passing vapours over a hot catalyst (silica or alumina) or mixing with steam at high temperatures ($600-700\text{ }^\text{∘}\text{C}$).

What is the balanced symbol equation for photosynthesis?

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$$

Briefly explain the greenhouse effect.

The Earth absorbs radiation from the sun and emits it as infrared radiation, some of which is absorbed by greenhouse gases (like $CO_2$ and $CH_4$), warming the atmosphere.

What are the three main steps in making groundwater potable?

1. Sedimentation (sink large insoluble particles), 2. Filtration (remove small insoluble particles), 3. Chlorination (kill microbes).