In order to calculate the number of neutrons you must subtract the from the

Explanation:

The nucleus of an atom is consituted by protons and neutrons. The electrons are out of (surrounding) the nucleus.

The elements are uniquely identified by the atomic number, which is the number of protons.

Since, the mass of the electrons is barely 1 / 1840 times the mass of the protons or neutrons, the mass of the atoms is approximated to the mass of protons and neutrons. The relative mass of neutrons and protons is practically 1.

So, the mass number of an atom is the sum of the protons and neutrons.

The symbols and equation used are:

Hence, to calculate the number of neutrons, N, you solve from that equation:

Which means that to calculate the number of neutrons you subtract the atomic number from the mass number.

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

the volume increases