Sodium (Na) reacts with nitrogen gas (N2) to produce sodium nitride. If a student collects 2.5 moles of sodium nitride (NaN3) after the reaction has been completed, determine the number of moles of nitrogen that were initially present.

2Na + 3N2 -> 2NaN3

Your

3.75 mole N2

1.2 mole N2

3.87 mole N2

Answer : The correct option is, 3.75 mole

Explanation : Given,

Moles of = 2.5 mol

The balanced chemical equation is:

From the balanced reaction we conclude that

As, 2 moles of produce from 3 moles of

So, 2.5 moles of produce from moles of

Therefore, the moles of initially present was, 3.75 moles.

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

confused

confused             hewdejdnjnjsnd