At 0.750 atm, the volume of a gas is 300.0 ml. if the temperature remains constant and the pressure is changed to 0.600 atm, what is the new volume of the gas? 0.00150 ml 0.00200 ml 155 ml 375 ml

375

Explanation: just took the test

- 375 mL, last choice is correct.

Solution:- The problem is based on Boyle's law. From this law, At constant temperature the volume of the gas is inversely proportional to the pressure.

The equation used for this gas law is:

is initial pressure, is final pressure.

is initial volume and is final volume.

From given data, the initial pressure is 0.750 atm, initial volume is 300.0 mL.

Final pressure is 0.600 atm and we are asked to calculate the final volume.

Let's plug in the values in the equation:

Let's rearrange this for final volume.

= 375 mL

So, the new volume of the gas is 375 mL, last choice is correct.

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

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