C5-Chemical Changes Flashcards
Meals can be placed in order of reactivitty …
by their reactions with water and dilute acid .
How do Potassium , SOdiuma nd Lithiumr eact iwth ater
very rapidly produce alkaline solutions .
Dilute acids - dangerously explode
How does magnesium ,aluminumm , zinc iron react ith water
very slow reaction .
dilute acids - fizz give off h ydrogen gass and forms alt .
How do tin and lead react with water ?
slight reaction with steam ,
dilute acids - slowlh
hwo do copper silver gold reaction water
no reactio evenw ith steam .
dilute acids no reaction
How do you work out the reactivityof a metal .
-When metals react , they lose electons and form positive ions .
-the reacticity of it a metal depends on its ability to lose electrons and form a positive ion
Potassium has the biggest aiity to form a positive ion and copper with the least.
What is the displacement rule ?
-A more reactive element will push put (displace) a less reactive element from its compound .
Magnesium + Iron oxide —> Magnesium oxide6Iron .
What is oxidation ?
Loss of electrons .
What is Reduction ?
Gain of electrons .
Check sheet and see what elements have eben oxidised and what has gained electrons write half euqaions .
-zinc has een oxidised
-copper has .been reduced
Unreactive metals are …
Like Gold aare found in the Earths crust as the metal itself (as Gold is so unreactive ) .
Metls react with oxygen …
to form compounds
Iron Oxidde Copper Oxide .
What cna displace Iron ?
Any metlas more reactive than Iron can dispalce Iron
State the products
What is oxidised
and what is reduced in this reaction ?
Lithim +Magnesium Oxide—>
Lithium Oxide + Magneisum .
Lithiumm gains oxygen so is being oxidiised
and magensiumm is reduced
What are the three acids used a lot in Chemistry ?
Hydrochloric acis HCL
Sulfuric Acid H2S04
Nitric Acid H2O3
All acids contain hydrgoen .
How can hydrogen be displaced ?
All metals higher than hydrogen can dispalce hydorgena s it is more rective than hydrogen /
acid +metal
—> salt +hydrogen
What two Salts do u need to know ?
Hydrochloric Acid - salt formed - Choride CL-ions
Sulfuric accid -salt form-Sulfate S042- ions
What three metals can you be asked , reaction with hydrochloric acid and sulfuric acid .
Magnesium , zinc and iron .
write the reactions with sulfuric acid and hydrochloric acid for magnesium , zinc and iron .
Check sheet .
HCL HAS 2 INFRONT OF IT .
How does magnesium react with acid why ?
Rapdily , as magneisum is a lot more reactive than hydrogen . And easily forms magnesium 2+ ions .
How does Zinc react with hydrogen ?
Quie rapidly as Zinc is more reactive . ANd quiet easily forms Zn2+iions .
How does Iron rect with Hydrogen ?
Iron reacts filry slowlyw ith acid , as iron is onl slightly more reactive than hydrogen . IRON LESS EASILY FORMS 2+IONS .
What are acids ?
Acids produces HydrogeN ions (h+) in an aqueous solution .
based on acid defenition , how does hydrochloric acid split ?
HCL—> H+ + Cl-
Based on acid defenition , how does sulphuric acid split ?
H2SO4—>2H+ +So4two minus .
Foor hydrochloric acid reavtion with zinc , iron and magnesium , what is oxidisied what is reudced ?
Chec sheet
Magnesium , iron , zinc (metals) loose electrons they are OXIDISED .Looses two .
Hydrogen is Reduced gaisn two electrrons .
(write all of them out )
What is the required practial about ?
How to make soluble salt using an acid .
What is a salt ?
A salt is compoound formed when spme of the hydrogen in an acid is repalced by a metal .
a salt is made from a positive metal ions and a negative ion from an acid .
RQP What is the positive ion , what is the negative ion .
Copper Oxide +Sulfuric Acid —> Copper Sulfate +water
Metal[positive ion Cu2+
Negative ion -So2- you need sulphuric acid to make this
Can be done using COPPER OXIDE OR COPPER CARBONAE , SAME STEPS .
First stage of RQP ?
Start with a fixed volume of dilute sulfuric acid .
-this is a limiting reactant .
Why is the sulfuric acid a limtiign reactant ?
-As we don;t want any excess ulfuric acid as it can contaminate our salt .
Second stage of RQP ?
Gently heat acid until its almsot boiling (dont want ubbling over as it dangerous when adding oother reactan ).
Third stage of RQP ?
Using a spatula , add small amounts of copper oxide to the acid .
fourth stage of RQP ?
stir solution using a glass rod .
fifth stage of RQP ?
Copper oxide will react and seem to disappera .
-Solution will turn blue colour , colour of copper sulfae ,
-continue adding copper oxdie if solotuion continues to be a clear blue .
sixth stage of RQP ?
stop adding copper oxide if some powder remains after stirring .
-at this point , reaction has topped all acid has reacted .
seventh stage of RQP ?
Using filtiration , remove any unreaced copper oxide .
eigth stage of RQP ?
Take copper sulfate solution and palce in evaporating bain .
-Genlt heat over beaker of boiign ater , heat until half of solution remains .
ninth stage of RQP ?
-Leave solution for 24 hrs in cool place for copper sulfate crystals to form .
-Scrape crystals into paper townel , gently pat dry and no ou have pure dry copper sulfate crystals .
Equipment needed for the RQP ?
-Heat proof mat
Tripod
Bunsen burner
Gauze
Beaker
FILITRIRATION Filter paper and filter funnel
Copper oxide is a bblack powder .
What is this RQP an example of ?
Neutralisation
Acid+base —> salt +water
also same for CARBONATE
Acid+Carbonate —> a salt+water +carbondioxide
What are bases ?
Bases are chemiclas which can neutralise acids and porduce salt + water.
Bases are usually meal oxides or metal hydroxides .
Whata re alklais ?
Bases that are soluble in water . (sodium hydroxide) is a base and an alkali .
What do alkalis produce is aqueous solution (oH-)
Sodium Hydroixde : NaOH—> NA+ OH-
What are the rpducts
Nitric acid +lithium hydroixxide
Lithium nitrate and water .
nitric acids forms nitrates
acid +alkali
—> salt +water
acid +carbonate
—> a salt + water + caarbondioxide
examples of carbonates ?
Sodium Carbonate
Calcium Carbonate
Potassium Carbonate
all contian a metal ion
hydrochlroic aicd+sodium carbonate
—> sodium chlirde +water+carbon dioxidie
do the same form calcium carbonate
and potassim carbonate .
Predict the products
Hydrochloric acid +Copeprcarbonate —>
Copper Chirde+Water+Co2
What is the Ph scale ?
Ph sclae tells us the acidity or alkalinity of a soloution
eiehther we use a pH proble (electronically ) or universlsal indictor (changes color dpeending or acidic , alkaline or neutral ).
Universal Indicator Colours ;
Green -neutral
Colours toward red - acidic
colours towards purple -alkaline
acids have a ph …
less than 7
solutions with a ph of 7 are …
neutral
solutions witha ph 8-14
are alkaline ,
reaction betwene acids and alkalines ?
NEUTRALISIATION EQUATION ACC
acids produce Hdrogen ions form H+ ions in aquoeus solutions
alkalnes Hydroixide ions form Oh-ions
H+ + OH—-> water
hydrogen and hdyroxide ions form water .
What are strong acids ?
Strong cids fully ionise in aqueopus soltioions .
(Lower Ph than weak acidd as hydrgogen ions fully ionise ) due to one way arrow —>.
What are weak acids ?
Partially ionise in aqueous solotuions .
(higher ph)
Ph scale gives idea of cocnentration of hydrogen ions .
arrow reversible reaction shows not alla cid molecules fully ionise .
example of strong acid
hydrochloric acid
sulfuric acid
nitric acid
example of weak acids
carbonic acid
ethanoic acid
citric acids
Why do stronger acids have a lower ph than weak acids ?
BECAUSE , strong acids fullyy ionise , porducing a greater concentration of h ydrogen ions than weak acids .
As the PH scale decreses by one unit …
the concentration of hydroge ions increase by ten times .
ph1 has a 10x greater concentrtion than ph2 ONE ORDER OF MAGNITUDE AKAA AS .
and has a 100x greater concentration than ph3 TWO ORDERS OF MAGNITDE AKA AS
wHAT ELSE IS PH EFFECTED BY ?
tHE COCNENTRATION OF AN ACID ,M TELS US THE AMOUNTO F ACID MOLECULES INA GIVEN VOLUME OF SOLUTION .
-a DILUTE ACID WILL HAVE FEWE CID MOLECULES IN A GIVEN VOLUEME THAN A COCNENTRACED CID , EVEN IF THE STENGTH OF THE ACID IS THE SAM E.
