Asystem undergoes a two-step process. in step 1, it absorbs 50. j of heat at constant volume. in step 2, it releases 5j of heat at 1 atm. as it returned to its original internal energy. find the change in the volume of the system during the second step and identify it as an expansion or compression.

Expansion.

Explanation:

In step 1:

Since, volume is constant.

Therefore, Work Done , w=0.

q= 50\ J.

We know equation of thermodynamics,

Step 2:

Heat is released therefore,

As system returned to its initial state.

Therefore,

So, Work Done,

Also,

Therefore,

Since, is positive.

Therefore, it is expansion.

Hence, this is the required solution.

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

b) nuclear ive learned that in a pedtrodic table