Jonas mixes citric acid with baking soda. how does he know the reaction is endothermic?

Endothermic reaction absorbs heat and an exothermic reaction releases heat. After Jonas mixes citric acid with baking soda, heat is required to start the reaction. Therefore it is an endothermic reaction and not an exothermic one. Endothermic reactions do not start spontaneously they need heat to start the reaction.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm

what is the question?