Topic 6 Flashcards
describe what you would see if damp, blue litmus paper is placed into chlorine gas
turns red and is then bleached white
when the gas hydrogen chloride is dissolved in water a solution forms. blue litmus paper dipped into the solution turns red.
state why the litmus paper turns red
solution is acidic (hydrogen ions)
sodium reacts with water to form sodium hydroxide solution and hydrogen.
complete the balanced equation and state symbols:
—Na(-) + 2H2O(-) —> —NaOH(-) + H2(-)
2Na(s) + 2H2O(l) —> 2NaOH(aq) + H2(g)
in an experiment equal sized pieces of sodium, lithium and potassium are added to separate samples of water. a flame is produced only with potassium because potassium:
A) is the softest metal
B) has the lowest melting point
C) is the most reactive
D) is the only flammable metal
C - is the most reactive
explain in terms of electronic configuration the increase in reactivity from lithium to sodium to potassium
atoms become larger so outer electrons more easily lost
describe what is seen when chlorine water is added to potassium bromide solution and the mixture shaken
a colourless potassium bromide solution and the mixture turns orange
chlorine reacts with potassium bromide to form potassium chloride and bromine. in this reaction chlorine forms chloride ions.
Cl2 + 2KBr —> 2KCl + Br2
in this reaction chlorine has been reduced. explain using the equation how you know that chlorine has been reduced
chlorine gains an electron to from a negative chloride ion
write the half equation for the formation of bromine from bromide ions
2Br- —> Br2 + 2e
aluminium reacts with chlorine to form aluminium chloride.
write the balanced equation for this reaction
2Al + 3Cl2 —> 2AlCl3
chlorine reacts with hydrogen to form hydrogen chloride
write the balanced equation for this reaction
Cl2 + H2 —> 2HCl
lithium, potassium and rubidium are alkali metals. describe what you would see when a small piece of rubidium is dropped on to water
fizzes and the rubidium disappears. an explosion is observed.
electronic configuration of:
lithium - 2,1
potassium - 2,8,8,1
lithium is less reactive than potassium
explain in terms of their electronic configurations why lithium is less reactive than potassium
outer electron is closer to the nucleus so more attraction for electron so the electron is harder to lose
describe the test to show a gas is chlorine
damp litmus paper goes white
bromine reacts with hydrogen to form hydrogen bromide. hydrogen bromide dissolves in water to form a solution.
state the name of the solution formed
hydrobromic acid
there is a trend in the colour and state of the halogens at room temp. predict the colour and state of astatine at room temp
colour - grey
state - solid
bromine, chlorine and iodine are dissolved in water to make aqueous solutions. potassium iodide solution is added to each of these solutions.
BROMINE) initial colour - orange, final colour - brown
CHLORINE) initial colour - pale green, final colour - brown
IODINE) initial colour - brown, final colour - brown
explain the observations
chlorine and bromine are more reactive than iodine. chlorine and bromine displace iodine. the brown final colour is due to iodine
fluorine reacts vigorously with iron to produce iron (III) fluoride, FeF3+
write the balanced equation for this reaction
2Fe + 3F2 —> 2FeF3
potassium reacts with fluorine to form potassium fluoride. potassium fluoride is a solid. complete the balanced equation and add state symbols
—K(-) + F2(g) —> —KF(-)
2K(s) + F2(g) —> 2KF(s)
sodium iodide solution is colourless. when a solution of bromine is added to sodium iodide solution, a reaction occurs
2NaI + Br2 —> 2NaBr + I2
the mixture turns brown. give the name of the substance causing the brown colour
iodine
sodium iodide solution is colourless. when a solution of bromine is added to sodium iodide solution, a reaction occurs
2NaI + Br2 —> 2NaBr + I2
explain which substance has been reduced in this reaction
bromine because electrons are gained
why is rubidium more reactive than potassium?
A) the metallic bonds in rubidium are weaker than those in potassium
B) rubidium is a softer metal than potassium
C) the outer electron of a rubidium atom is further from the nucleus than potassium’s
D) rubidium has a more exothermic reaction with water than potassium does
C - the other electron of a rubidium atom is further away from the nucleus than potassium’s
the density of a gas can be found with density = mass / volume
a student carried out an experiment to find the density of argon. the mass of a stopper and flask, containing no gas, was known. the flask was completely filled with argon and its mass measured.
mass of stopper and flask in g - 78.639
mass of stopper and flask of argon in g - 79.120
volume of flask in cm3 - 250
use results to calculate density
79.120 - 78.639 = 0.481
d = 0.481 / 250
= 0.001924 g cm-3
the flask used for the experiment holds 250.0 cm3 when filled up to the line. there is an error in the volume that the student has used in the calculation. this would give an incorrect value for the density of argon.
identify this error and state what should be done to correct it.
ERROR - the volume of the flask is more than 250cm3
WHAT SHOULD BE DONE - measure the whole volume of the flask
four of the noble gases are argon, helium, krypton and neon
give these gases in order of increasing density
helium, neon, argon, krypton
