Answer: D (the balance and the Styrofoam beaker only). This experiment measures a temperature change (an enthalpy effect), not a rate, so timing the reaction is irrelevant. You record only the starting and final temperatures, so a stopwatch is not needed. A gas syringe measures the volume of gas evolved over time, which again belongs to rate experiments, not to measuring heat released.
You do need a balance, because the sodium carbonate is the limiting reactant and its mass must be known accurately. You also need the Styrofoam (polystyrene) beaker: it is a good insulator that minimises heat loss to the surroundings, giving a more accurate temperature change for this exothermic neutralisation.
So items 3 and 4 only are required. Common error: students include the stopwatch by habit, but timing only matters when measuring rate, not when measuring \(\Delta T\).
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