Given the following reaction: 2 ZnS(s) + 3 O2(g) → 2 ZnO(s) + 2 SO2(g) ΔH = -927.54 kJ

How much energy would be released if 50.0g of ZnS(s) is reacted with 30.0g of O2(g)?

-354.78 kJ of energy would be released for a given amount.

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass.

The equation used is:

    ......(1)

For Zinc:

Mass of zinc = 50.0 g

Molar mass of zinc = 65.38 g/mol

Plugging values in equation 1:

For oxygen gas:

Mass of oxygen gas = 30.0 g

Molar mass of oxygen gas = 32 g/mol

Plugging values in equation 1:

The chemical equation follows:

By the stoichiometry of the reaction:

If 2 moles of zinc reacts with 3 moles of oxygen gas

So, 0.765 moles of zinc will react with = of oxygen gas

As the given amount of oxygen gas is more than the required amount. Thus, it is present in excess and is considered as an excess reagent.

Thus, Zn is considered a limiting reagent because it limits the formation of the product.

By the stoichiometry of the reaction:

If 2 moles of zinc are releasing 927.54 kJ of energy

So, 0.765 moles of zinc will react with = of energy

Hence, -354.78 kJ of energy would be released for a given amount.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol