Use the periodic table to determine the electron configuration for aluminum (al) and arsenic (as) in noble-gas notation.

Electronic configuration of

1. Aluminium is

2. Arsenic is

Explanation: To write the electronic configuration of the elements in the noble gas notation, we first count the total number of electrons and then write the noble gas which lies before the same element.

Atomic number = 13

Total number of electrons = 13

Noble gas which lies before this element is Neon (Ne).

Neon has 10 electrons, rest 3 electrons are filled in 3s and 3p sub-shells.

Electronic configuration of Aluminium becomes

Atomic number = 33

Total number of electrons = 33

Noble gas which lies before this element is Argon (Ar).

Neon has 18 electrons, rest 15 electrons are filled in 4s , 3d and 4p sub-shells.

Electronic configuration of Arsenic becomes .

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