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# So say I was doing your bog-standard magnesium and HCl reaction... watch

1. I'm measuring the temperature change of the HCl which would increase right? And what things apart from heat escaping to the environment and measuring errors could cause the result to not be quite right??
2. (Original post by XShmalX)
I'm measuring the temperature change of the HCl which would increase right? And what things apart from heat escaping to the environment and measuring errors could cause the result to not be quite right??
You are going to calculate the value of ΔH from the equation:

ΔH = mcΔT

and then divide by the number of moles reacted:

ΔH/mol = mcΔT/mol

so look for errors in every part of the equation..

Heating up the thermometer
Heating up the reaction vessel
Evaporation
Thermometer inaccuracy
Volume inaccuracy (or mass of liquids)
Hydrochloric acid/magnesium chloride solution SHC varying from that of water.
Gas escaping with heat energy
Mass of magnesium measured
Concentration of the HCl
3. (Original post by charco)
You are going to calculate the value of ΔH from the equation:

ΔH = mcΔT

and then divide by the number of moles reacted:

ΔH/mol = mcΔT/mol

so look for errors in every part of the equation..

Heating up the thermometer
Heating up the reaction vessel
Evaporation
Thermometer inaccuracy
Volume inaccuracy (or mass of liquids)
Hydrochloric acid/magnesium chloride solution SHC varying from that of water.
Gas escaping with heat energy
Mass of magnesium measured
Concentration of the HCl
And its exothermic so ΔH for HCl would be negative whilst q would be positive right?
4. Anyone?
5. the magnesium may have a layer of oxide on it.
6. (Original post by domino0806)
the magnesium may have a layer of oxide on it.
Ahhh that a REALLY good one thanks!
Does anyone know if its exothermic and if so if ΔH for HCl would be negative whilst q would be positive?
7. Is it exothermic and if so if ΔH for HCl would be negative whilst q would be positive?

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