1. How many moles are 1.50 x 10+25 atoms of phosphorous?
Show work!!

24.9moles

Explanation:

1mole of a substance contains 6.02x10^23 atoms.

It therefore means that 1mole of phosphorus also contains 6.02x10^23 atoms.

We, need to find the number of moles of phosphorus that contains 1.50x10^25 atoms.

This can be done below

If 1 mole of phosphorus contains 6.02x10^23 atoms,

Therefore Xmol of phosphorus will contain 1.50x10^25 atoms. i.e

Xmol of phosphorus = (1.50x10^25)/6.02x10^23 = 24.9moles

Therefore, 24.9moles of phosphorus contains 1.50x10^25 atoms

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