Predicting Chemical Reactions (OCR GCSE Chemistry A (Gateway)): Flashcards

The halogens are the Group 7 non-metal elements: fluorine, chlorine, bromine, iodine and astatine. They are all poisonous and each has seven electrons in their outermost shell.

Going down Group 7, atoms get larger, which increases intermolecular forces between molecules. More energy is needed to overcome these forces, so melting and boiling points increase.

True.

All halogens exist as diatomic molecules (e.g. Cl₂, Br₂). The two halogen atoms share electrons, forming a single covalent bond.

The reactivity of Group 7 halogens decreases as you go down the group, because the attraction between the nucleus and the outermost shell decreases.

A halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide. For example, chlorine displaces bromine from potassium bromide solution.

Chlorine is a pale yellow-green gas, bromine is an orange-brown liquid and iodine is a grey-black solid. The halogens become darker in colour going down the group.

True.

Chlorine is more reactive than bromine, so it displaces bromine from potassium bromide solution. Bromine is produced, turning the solution orange.

A halide ion is a negatively charged ion formed when a halogen atom gains one electron during a reaction. Halide ions carry a –1 charge (e.g. Cl^-, Br^-, I^-).

Fluorine is the smallest halogen, so its outermost shell is closest to the nucleus. This means its attraction for an incoming electron is strongest, making it the most reactive halogen.

When halogens react with metals, they form ionic compounds called metal halide salts, where the halide ion carries a –1 charge.

The noble gases are the Group 0 elements: helium, neon, argon, krypton, xenon and radon. They are all monatomic, colourless, non-flammable gases at room temperature.

The noble gases are unreactive because they have full outer shells of electrons. This configuration is extremely stable, so they have no tendency to gain or lose electrons in chemical reactions.

True.

Going down Group 0, atoms become larger, increasing intermolecular forces. More energy is required to overcome these forces, so boiling points increase down the group.

Helium is used to fill balloons because it is less dense than air and does not burn.

Argon is used in welding because it is chemically inert. It provides an unreactive atmosphere that prevents the hot metal from reacting with oxygen or nitrogen in the air.

The density increases going down Group 0. Each successive noble gas has a greater relative atomic mass, making the individual atoms heavier and the gas denser.

True.

Helium has only 2 electrons in total, filling its first and only shell. The other noble gases all have eight electrons in their outermost shell.

Monatomic means existing as single, individual atoms rather than in molecules. All noble gases are monatomic because their full outer shells make bonding with other atoms unnecessary.

Neon, argon and xenon are used in advertising signs because they glow brightly when a high potential difference is applied under low pressure.

The transition metals are a block of metallic elements located between Groups 2 and 3 in the periodic table. They are hard, dense, lustrous metals with high melting points and good electrical conductivity.

Transition metals can act as catalysts because they can form ions with different charges. For example, iron is used as a catalyst in the Haber Process to speed up the production of ammonia.

False.

Transition metals themselves are not colourful — it is the compounds they form that display a range of colours in aqueous solution.

Iron is used as a catalyst in the Haber Process, and vanadium pentoxide is used in the Contact Process to produce sulfuric acid.

1. Transition metals are much harder, stronger and denser than Group 1 metals, and they have far higher melting points.\n2. Transition metals are also much less reactive — they react slowly or not at all with water and oxygen, whereas Group 1 metals react vigorously.

Transition metals can form ions with different charges (e.g. iron can form Fe²⁺ or Fe³⁺). This gives their compounds different properties and colours, and is why transition metals are useful as catalysts.

True.

Group 1 metals lose their outer electron more easily as atomic size increases, so reactivity increases. Group 7 non-metals attract electrons less strongly as size increases, so reactivity decreases.

Iron is far less reactive than Group 1 metals. A Group 1 metal tarnishes within seconds of exposure to oxygen, while iron can take several weeks to form iron oxide (rust) and also requires the presence of water.

Group 1 metals always form ions with a +1 charge, whereas transition metals can form ions with variable charges.

1. Transition metals are lustrous (shiny) and highly dense, with very high melting points.\n2. They are hard and strong, and are good conductors of heat and electricity.

The reactivity series is an ordered list of metals ranked by how easily they lose electrons to form positive ions. More reactive metals are higher in the series and react more vigorously with water and acids.

When a metal reacts with cold water, the products are a metal hydroxide and hydrogen gas. The general equation is: metal + water → metal hydroxide + hydrogen.

True.

In a displacement reaction, the more reactive metal takes the place of the less reactive metal. For example, zinc displaces copper from copper sulfate solution because zinc is more reactive.

When a metal reacts with a dilute acid, the products are a metal salt and hydrogen gas.

Carbon is included because it is a cheap reducing agent that can extract metals from their oxide ores — metals below carbon can be extracted this way. Hydrogen is included to help predict whether a metal can displace it from water or acids.

The more reactive a metal, the more easily it loses electrons to form positive ions. Reactivity is directly related to the tendency to become an ion — highly reactive metals lose electrons very readily.

Carbon is included because it is a cheap reducing agent that can extract metals from their oxide ores — metals below carbon can be extracted this way. Hydrogen is included to help predict whether a metal can displace it from water or acids.

A displacement reaction occurs when a more reactive metal takes the place of a less reactive metal in a compound. The more reactive metal becomes the ion and the less reactive metal is released.

The more reactive a metal, the more vigorous the reaction with water or acid, because hydrogen is produced at a greater rate.

Zinc displaces copper from copper(II) oxide because zinc is more reactive. The products are zinc oxide and copper metal: Zn + CuO → ZnO + Cu.