When 0.702 g of Ca metal is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 114C is observed.

Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.
(Note: Pay attention to significant figures. Do not round until the final answer.)
The molar heat of reaction, H rxn, for the reaction of

Ca(s) + 2H+(aq) Ca2+(aq) + H2(g)
is .....kj/mol

q = mass water x specific heat water x delta T.

Then q/0.702 gives J/g and multiply by atomic mass Ca to get J/mol, then divide by 1000 to convert to kJ/mol.

But there is no water involved...

What do you think 0.500 M HCl(aq) is? That's 200 mL of 0.5 M HCl(aq) which is mostly water. Only 3.65 grams is HCl. And they specify that the density is 1.00 g/mL so that is 200 g for water. Also, the 4.184 J/g*C listed in the problem is the specific heat for WATER.

Owned.

When I did the question, i noticed my answer had to be negative. why was that?

HAHA YOU GOT OWNED

To find the molar heat of reaction, we can use the equation:

q = m * C * ΔT

where:
q is the heat transferred in Joules (J)
m is the mass of the substance in grams (g)
C is the heat capacity in J/g°C
ΔT is the change in temperature in °C

In this case, we need to find the heat transferred (q). We know the heat capacity of the solution is 4.184 J/g°C, the change in temperature (ΔT) is 114°C, and the mass of calcium (Ca) is 0.702 g.

First, let's find the heat transferred (q):

q = (0.702 g) * (4.184 J/g°C) * (114°C)
q = 331.50256 J

Next, we need to convert the heat transferred (q) to kilojoules (kJ) since we are looking for the molar heat of reaction in kJ/mol.

1 kJ = 1000 J

Therefore:

q = 331.50256 J * (1 kJ / 1000 J)
q = 0.33150256 kJ

Now, let's calculate the molar heat of reaction using the balanced equation:

Ca(s) + 2H+(aq) → Ca2+(aq) + H2(g)

From the balanced equation, we can see that 1 mole of Ca reacts with 2 moles of H+ to produce 1 mole of Ca2+ and 1 mole of H2.

The moles of Ca reacted can be calculated using its molar mass:

Molar mass of Ca = 40.08 g/mol

moles of Ca = mass / molar mass
moles of Ca = 0.702 g / 40.08 g/mol
moles of Ca = 0.0175 mol

From the balanced equation, we see that for every 1 mole of Ca reacted, ΔH is -2 moles of H+ ions. Therefore, the moles of H+ ions can be calculated as:

moles of H+ = 2 * moles of Ca
moles of H+ = 2 * 0.0175 mol
moles of H+ = 0.035 mol

Finally, we can find the molar heat of reaction (ΔH) using the equation:

ΔH = q / moles of H+

ΔH = 0.33150256 kJ / 0.035 mol
ΔH = 9.47293086 kJ/mol

Therefore, the molar heat of reaction (H rxn) for the reaction is approximately 9.47 kJ/mol.