C5 - Energy Changes Flashcards
Give two examples of exothermic reactions
Combustion
Neutralisation
Two everyday uses of exothermic reactions
Some hand warmers
Self heating cans
Everyday use of endothermic reaction
Sport injury packs
How could you investigate the effect of acid concentration on the energy released in a neutralisation reaction between hydrochloric acid and sodium hydroxide ( 6 marks)
Put 25cm^3 of 0.25mol/dm^3 of hydrochloric acid and sodium hydroxide in separate beakers
Place beakers in a water bath set to 25°C until they are both at the same temperature
Add the HCl followed by the NaOH to a polystyrene cup with a lid
Take the temperature of the mixture every 30 seconds and record the highest temperature
Repeat using different concentration i.e. 0.5mol/dm^3 and then 1mol/dm^3
The reaction is higher than the products is this exothermic or endothermic
Exothermic
The products is higher than the reactants is this exothermic or endothermic
Endothermic
Substance - Melting point
Water - 0 fr..
Sodium Chloride - 801 why we melting salt bruh
Diamond - 3550
Explain the melting points and refer to structure and bonding
Water:
Weaker intermolecular forces between molecules
Small amounts of energy required to overcome forces
Hence low melting point
Sodium Chloride:
Giant ionic lattice
Many strong ionic bonds
Large amounts of energy required to break bonds
Middle melting point
Diamond:
Giant covalent structure
Many covalent bonds between atoms
Very large amount of energy required to break bonds
Highest melting point
Yea allat fr.
Substance - Melting point
Water - 0 fr..
Sodium Chloride - 801 why we melting salt bruh
Diamond - 3550
Water:
Weaker intermolecular forces between molecules
Small amounts of energy required to overcome forces
Hence low melting point
Sodium Chloride:
Giant ionic lattice
Many strong ionic bonds
Large amounts of energy required to break bonds
Middle melting point
Diamond:
Giant covalent structure
Many covalent bonds between atoms
Very large amount of energy required to break bonds
Highest melting point
Yea allat fr.
Describe a safe method for making pure crystals of copper chloride from copper oxide and dilute hydrochloric acid ( 6 marks)
Warm 25cm^3 of hydrochloric acid in a beaker using a Bunsen burner
Add 5cm of copper oxide using a spatula
Add until all the acid has reacted
Filter excess copper oxide using funnel lined with filter paper to get salt solution
Dry crystals using warm oven
Explain how you could adapt the temperature change investigation (poly cup one fr) to verify reactivity of metals
Use metal instead of hcl acid
Repeat using different metals shown
Compare the mean temperature changes of the metals
More reactive the metal, greater the temperature change
Explain the difference between the strength and concentration of an acid (2 marks)
Strength is the proportion of the acid molecules that ionise in water
Concentration is the total number of dissolved acid molecules (per unit volume)
Is breaking bonds the reactant side or the product side
reactants
If overall energy change is negative is it endothermic or exothermic
Exothermic
Describe the exothermic graph in terms of sloping cuz no photos here fr..
reactants slope down to products
Describe endothermic graph in terms of sloping
reactants slop up towards products
