in an experiment a student mixes a 50.0 ml sample of 0.100 m agno₃ (aq) with a 50.0 ml sample of 0.100 m nacl(aq) at 20.0°c in a coffee-cup calorimeter. which of the following is the enthalpy change of the precipitation reaction represented above if the final temperature of the mixture is 21.0°c? (assume that the total mass of the mixture is 100. g and that the specific heat capacity of the mixture is 4.2 j/(g.° (a) -84 kj/mol, (b) -0.42 kj/mol (c) 0.42 kj/molu (d) 84 kj/molpx

The enthalpy change during the reaction is -84 kJ/mole.

Explanation:

First we have to calculate the heat gained by the solution.

where,

Q = heat gained = ?

m = mass of the solution = 100.0 g

c = specific heat =

= final temperature =

= initial temperature =

Now put all the given values in the above formula, we get:

Now we have to calculate the enthalpy change during the reaction.

where,

= enthalpy change = ?

Q = heat gained = 420 J

n = number of moles silver nitrate= n

Molarity of the silver nitrate solution = M = 0.100 M

Volume of the silver nitrate solution = V = 50.0 mL = 0.050 L

(1 kJ = 1000 J)

Therefore, the enthalpy change during the reaction is -84 kJ/mole.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !