C7 Exothermic Reactions Flashcards
Complete word equation for reaction
Copper sulfate + water
One observation during step 4 which shows copper carbonate is in excess
Residue of copper carbonate at the bottom of beaker
Give 1 reason for filtering mixture in step 5
To remove excess copper
Name equipment that can be used to warm filtrate gently in step 6
Bunsen burner
Calculate mass of salt actually produced
92.8 = mass/12.5 x 100
0.928 x 12.5 = 11.6
Give one reason why copper and metal is no used for sulfuric acid reactants
Copper - low reactivity, takes long to react
Sodium - high reactivity so reacts aggressively with sulfuric acid which is a hazard
Give 1 similarity and one difference between electronic structures of sodium and potassium
Similarity - both have 1 electron in outer shell
Difference - sodium has 2 full shells, potassium has 3 full shells
2 observations made when potassium reacts with water
Lilac flame
Potassium floats in water
What colour is universal indicator when added to potassium hydroxide solution
Blue/purple
Potassium hydroxide has OH- so is alkali
Estimate density of krypton
3.5-3.9
Which combination of solutions produces a reaction when mixed
Chlorine and potassium bromide
Which describes trend going down group 7
Molecular mass increases and boiling point increases
Name models of atoms shown in figure 2
Plum pudding model
Nuclear model
Compare plum pudding with atom today
Plum pudding has positive charge sphere - atom today as positive nucleus
Atom today has shells surround electrons
Atom today has neutrons, haven’t been discovered yet
Isotopes
Same number of protons and electrons but different number of neutrons
Explain results shown in figure 3
At 0g it is 21°C coz room temperature
Between 0g and 0.8g it increases as more zinc reacting
0.8g and 1g had same temp showing highest temp reached between these points
After 1g highest temp decreased as zinc in excess and solution gaining greater mass
Why using polystyrene cup gives more accurate results than glass beaker
Polystyrene cup holds heat better causing heat output reaction to be more accurate
Complete ionic equation between zinc and copper sulfate solution
Zn2+(aq) + Cu(s)
1 reason for random errors in this experiment
Copper sulfate initial temp may be different
Describe what happens to calcium atoms and chlorine atoms when ionic compound calcium chloride is formed
Calcium loses 2 electrons to form Ca2+
Chlorine gains 1 electron to form Cl-
These electrostatically attract to form calcium chloride
Solid calcium chloride cannot be electrolysed
Give 1 reason why
Ions cannot flow and carry charge in a solid
Name product formed at negative electrode calcium chloride electrolysed
Hydrogen
What is half equation for reaction at positive electrode when calcium chloride solution electrolysed
2Cl- ————> Cl2 + 2e-
Copper chromate solution contains the ions Cu2+ and CrO4 2-
Explain results shown
Copper is blue, chromate is yellow
Copper is positive ion so attracted to negative electrode
Chromate is negative ion so attracted to positive electrode
Symbols the 5 metals in table 3 order of reactivity
Copper
Magnesium
Nickel
Silver
Zinc
Mg, Zn, Ni, Cu, Ag
How hydrogen fuel cells produces a potential difference
Hydrogen lose electrons at anode
which flow through a circuit
Oxygen gains electrons at cathode forming water
How iron conducts thermal electricity
Iron is transition metal metal so it’s delocalised electrons can carry thermal energy through metal
Explain why mixing iron with other metals makes alloys harder than pure iron
Iron and other metals have different sized atoms meaning other metals distort irons layers which makes it harder for layers to slide over each other
Correct equation for reaction iron reacts with chlorine
2Fe + 3Cl3 ————> 2FeCl3
Ratio of numbers of ions in Fe3O4
1Fe2+ : 2Fe3+ : 4O2-
Why propene has low boiling point
Has simple molecular structure meaning it has weak intermolecular forces that are easy to overcome
Which is the correct reaction profile and labels for reaction between oxygen
B
What is meant by weak acid
Acid that partially ionises in solution
What happens to pH of an acid as acid is diluted with water
Concentration on H+ ions dcreases therefore neutralising acid
Give 3 more steps the student must do before adding acid to alkali from burette
Use volumetric pipette to measure volume of alkali
Place alkali into conical flask
Add indicator
Calculate volume of hydrochloric acid in cm3 needed in titration
0.0045 ➗ 0.15 = 0.3dm
0.03 x 1000 = 30cm
Why calcium reacts more vigorously than magnesium with hydrochloric acid of same concentration
Calcium is more reactive than magnesium
Calcium’s outer electrons are further from nucleus, so attraction between nucleus and electron is weaker
This makes it easier for calcium to lose electrons and react
Calculate mean temperature reached
Include an uncertainty in your answer
37.5 +- 3
