EXAM QUESTIONS Flashcards
Describe what happens when a lithium atom reacts with a chlorine atom-4marks
Lithium is a metal and donates its valence electron and becomes a li ^+1 ion. The chlorine atom gains one electron in its outermost shell to form a chloride ion with charge ^ 1-. The oppositely charged atoms attract to form an ionic compound with ionic formula NaCl..,
What is the formula of sodium nitride?
Na3N
What flame test for testing a metal alkali produces Red flame?
Lithium
What flame test for testing a metal alkali produces Intense Yellow/Orange Flame?
Sodium
What flame test for testing a metal alkali produces Purple (Lilac/Violet) flame?
Potassium
What flame test for testing a metal alkali produces Brick Red flame?
Calcium
Covalent Bond Properties.
Explain Why Graphite is very soft?
Because the carbon is arranged in layers with weak dispersion forces between the layers, this allows the layers to slide over one another.
Explain Why Diamond is very Hard?
Because each carbon atom has 4 covelant bonds and thus they are very hard to break.
Explain How Graphite conducts electricity.
Because of the delocalized valiance, electrons that are free to move between the layers and carry charge.
State the force that exists between (HCI) Atom.
Dipole-Dipole Force.
Explain why this allow is harder than pure metal Y ?
Because in pure metal the cations are of the same size , but in an alloy cations are of different sizes , and thus this stops cations from sliding over one another.
Sate, what is meant by the term empirical formula?
Simplest whole number ratio formula.
Calculate the percentage of S In HS.
97.0%
Describe and explain how crude oil is separated into its fractions.
Heat oil.
Substances with high boiling points condense at the bottom and Substances with Low boiling points condense at the top of the fractionating column. Crude oil is evaporated. Its vapours condense at different. Temperatures. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms and a similar range of boiling of boiling points.
Define the term electrolysis.
Electrolysis is the breakdown of ionic compounds, molten or aqueous/dissolved in solution, by the passage of electricity.
Which bonds break when propane transitions from a liquid to a gas in the column?
Weak intermolecular forces/dispersion forces.
Why do longer hydrocarbon chains have a higher viscosity?
Because smaller molecules have shorter chains and are less likely to get entangled, however, molecules that have larger chains are more likely to get entangled.
Define viscosity?
Viscosity is a measure of a fluid’s resistance to flow.
define the term fractional distillation
Fractional distillation separates a mixture into a number of different parts, called fractions. A tall fractionating column is fitted above the mixture. The column is hot at the bottom and cold at the top.
Why can alkenes undergo addition reaction but alkanes cant?
Alkenes are unsaturated hydrocarbons and con undergo addition reactions, where as alkanes are saturated hydrocarbons and thus are not able to undergo addition reactions.
Sodium sulfide? formula
na2s
Sodium sulphate? formula
na2SO4
How are metals able to conduct electricity?
Because of the delocalised valiance, electrons can move through the structure and carry charge.
Why are metals malleable?
Metals can be bent and shaped as when metals are bent, hammered or pressed, layers of ions slip over one another.
How are metals able to conduct heat?
Because they have delocalised valiance electrons that can move faster and transfer thermal energy quickly and easily.
Why do metals have a high melting and boiling point?
Because the electrostatic forces of attraction between cations and delocalised electrons are strong and it requires a lot of energy to break them.
Define the term alloy?
An alloy is a mixture of two or more elements, one of which is a metal.
What is titration used for?
To find the concentration of a solution.
Define the term, Haber process
The Haber process is the name given to the industrial production of ammonia. Nitrogen and hydrogen are reacted together using an iron catalyst to produce ammonia.
Define the term electroplating?
Electroplating is a technique where a thin layer of a desired piece of metal is used to plate or coat another object.
Why do we electroplate objects?
Helps us protect against rust.
Improve apperance/make them look shiney.
It is cheaper to plate than to make it out of a particular metal.
Titration
Fill up a burette with acid. …
Use a pipette to add alkali to a conical flask. …
Add an indicator to the alkali dropwise ( 2-3 drops at a time). …
Get a retort stand and place the burette above and clonical flask below.
place a white title underneath the cloncial flask
Slowly add the acid into the alkali and swirl your flask slowy as adding akail …
Slow the adding of acid when the indicator changes colour. …
Stop adding acid when there is a permanent colour change. …
Record the titre. …
Repeat the titration until you have at least 3 concordant results
Explain interms of electronic structure why flourine is he most reactive element in (Group7)?
Flourine is the smallest atom in (Group). Fluorine has the most significant attraction between the nucleus and outer shell. Therefore, fluorine can gain an electron into the outer shell more easily.
