Topic 3 Flashcards
salts of metals can be prepared by reacting the metal with an acid to produce the salt and hydrogen.
describe the test to show the gas is hydrogen
light a splint and place over the test tube. if you hear a pop, then hydrogen is present (squeaky pop)
excess solid nickel carbonate is added to dilute sulfuric acid in a beaker.
nickel carbonate + sulfuric acid —> nickel sulfate + carbon dioxide + water
nickel sulfate is formed in solution. describe how a sample of pure, dry nickel sulfate crystals can be obtained from the mixture of nickel sulfate solution and excess solid nickel carbonate in the beaker.
mix nickel carbonate and sulfuric acid. then filter the mixture to get rid of the excess nickel carbonate. solution in evaporating basin over bunsen and water evaporates, heat leaving. crystals form
the hydrogen ion concentration in a solution is decreased by a factor of 10.
state how the pH of this solution changes
pH increases by one
X and Y are solutions of two different acids. the concentration of acid in each solution, in mol dm-3 is the same. solution X has a pH of 3.4 and solution Y has a pH of 4.4.
state what could be used to measure these pH values of 3.4 and 4.4
pH meter
X and Y are solutions of two different acids. the concentration of acid in each solution, in mol dm-3 is the same. solution X has a pH of 3.4 and solution Y has a pH of 4.4.
what is the concentration of hydrogen ions in solution X compared with that in solution Y?
A) ten times lower
B) lower by a factor of 3.3/4.4
C) higher by a factor of 3.3/4.4
D) ten times higher
D - ten times higher
an experiment is planned to record the change in pH as a powdered base is added to 50 cm3 dilute hydrochloric acid. the method suggested is:
1 - add dilute HCl up to the 50cm3 mark on a beaker
2 - add one spatula of the base and stir
3 - measure the pH of the mixture
4 - repeat steps 2 and 3 until the pH stops changing
state how you could change the method so that the amounts of dilute HCl and of the base can be measured more accurately
dilute hydrochloric acid - use a measuring cylinder
base - use a balance to measure mass of the base
during the experiment the pH changes from 2 to 10. if phenolphthalein indicator is added at the beginning of the experiment, a colour change occurs as the base is added.
state the colour change that occurs:
at start , at end
at start - colourless
at end - pink
during the experiment the pH changes from 2 to 10.
explain in terms of particles present why the pH increases during the experiment
hydrogen ions (H+) neutralised so the concentration of them fall, and OH- concentration increases
the word equation for the reaction between copper carbonate and dilute sulfuric acid is:
copper carbonate + sulfuric acid —> copper sulfate + carbon dioxide + water
complete the balanced equation for this reaction:
CuCO3 + — —> — + CO2 + H2O
CuCO3 + H2SO4 —> CuSO4 + CO2 + H2O
what is the chemical test to show that the gas is carbon dioxide?
A) bubble the gas through limewater, limewater turns cloudy
B) put damp blue litmus paper in the gas, litmus paper turns red
C) put a lighted splint into the gas, the splint is extinguished
D) measure the pH of the gas, pH = 4
A - bubble the gas through lime water, limewater turns cloudy
figure 4 shows a conical flask containing dilute sulfuric acid.
copper carbonate is added to the acid in the flask. the copper carbonate is added one spatula measure at a time until the reaction has finished.
state two observations that would show the reaction has finished
no more bubbles/fizzing
no further change in colour
dilute hydrochloric acid is a strong acid.
explain why dilute hydrochloric acid is described as a strong acid
hydrogen ions fully dissociate
1cm3 of hydrochloric acid of pH 2 is made up to a volume of 10 cm3 with distilled water. state the pH of the new solution
pH 3
magnesium oxide reacts with dilute hydrochloric acid to produce magnesium chloride solution and water.
MgO(s) + 2HCl(aq) —> MgCl2(aq) + H2O(I)
write the ionic equation for this reaction
MgO + 2H+ —> Mg2+ + H2O
in an experiment magnesium hydroxide powder is added in 0.1g portions to 25cm3 of dilute hydrochloric acid until the magnesium hydroxide is just in excess.
universal indicator paper can be used to test the pH of the solution after each addition of magnesium hydroxide.
give the name of an alternative piece of equipment that can be used to measure pH
pH meter
state and explain how the pH changes as the magnesium hydroxide is added to the dilute hydrochloric acid
increases pH until above 7. during the reaction the base neutralises the acid so the hydrogen ion concentration is reduced as there is excess OH- ions
molten zinc chloride is an electrolyte. which row shows the products formed at the anode and cat the cathode when molten zinc chloride is electrolysed?
A) anode - oxygen, cathode - zinc
B) anode - chlorine, cathode - hydrogen
C) anode - chlorine, cathode - zinc
D) anode - oxygen, cathode - hydrogen
C) anode - chlorine, cathode - zinc
which of the following is the reason why molten zinc chloride is an electrolyte?
A) it contains molecules that can move
B) it has a giant structure
C) it contains delocalised electrons
D) it contains ions that can move
D - it contains ions that can move
copper sulfate solution was electrolysed using copper electrodes. before the electrolysis, the masses of the electrodes were determined. after the electrolysis the electrodes were washed and their masses re-determined.
ANODE) mass before - 11.27, mass after - 10.42, change in mass = -0.85
CATHODE - mass before - 11.32, mass after - 12.17, change in mass = +0.85
explain these results
anode lost copper and cathode gained copper. at anode, copper atoms become copper ions and lose two electrons. at cathode copper ions became copper atoms and gain two electrons
when sodium sulfate solution is electrolysed, using inert electrodes , hydrogen is formed at the cathode.
write the half equation for the formation of hydrogen gas, H2+, from hydrogen ions, H+
2H+ —> H2 - 2e-
throughout the experiment the volume of hydrogen and the volume of oxygen are measured at two minute intervals. results shown in figure 2
time in minutes:
0) volume of hydrogen - 0, volume of oxygen - 0
2) volume of hydrogen - 4, volume of oxygen - 2
4) volume of hydrogen - 8, volume of oxygen - 4
6) volume of hydrogen - 12, volume of oxygen - 6
8) volume of hydrogen - 16, volume of oxygen - 8
describe using the data what the results show about the volumes of hydrogen and oxygen produced in this experiment
oxygen and hydrogen increase with time. the volume of hydrogen is double the volume of oxygen
molten lead bromide is electrolysed. the products of this electrolysis are:
A) hydrogen and bromine
B) hydrogen and oxygen
C) lead and bromine
D) lead and oxygen
C - lead and bromine
calcium nitrate and calcium carbonate are both ionic compounds. calcium nitrate mixed with water behaves as an electrolyte. calcium carbonate mixed with water does not behave as an electrolyte.
explain in terms of solubility and movement of ions this difference in behaviour
calcium nitrate is soluble so ions are free to move in a solution
when molten zinc chloride is electrolysed, zinc ions, Zn2+, form zinc atoms
write the half equation for this reaction
Zn2+ + 2e- —> Zn
