2.   use your periodic table to determine the number of protons, electrons and neutrons that are in the following elements:                                               a. bromine (br)    protons, electrons, neutronsb. aluminum (al)  protons, electrons, neutronsc. beryllium (be)      protons, electrons, neutrons

Protons are the positively charged particles, electrons are the negatively charged particle and neutrons are neutral particles.

The number of protons is same as the atomic number of element.

The number of electrons is equal to the number of protons as atom consists of same number of protons and electrons.

The number of neutrons is equal to subtraction of number of protons from mass number.

That is, Mass number - Number of protons = Number of neutrons.

a. Bromine ()

atomic number of bromine is 35. Thus, number of protons = 35

And, number of electrons  = 35

Number of neutrons  = Mass number - Number of protons

Mass number of bromine  = 79.9

Therefore, Number of neutrons  = which is approximately equal to 45.

b. Aluminum ()

atomic number of aluminium is 13. Thus, number of protons = 13

And, number of electrons  = 13

Number of neutrons  = Mass number - Number of protons

Mass number of aluminium  = 26.9

Therefore, Number of neutrons  = which is approximately equal to 14.

c. Beryllium ()

atomic number of beryllium is 4. Thus, number of protons = 4

And, number of electrons  = 4

Number of neutrons  = Mass number - Number of protons

Mass number of beryllium  = 9

Therefore, Number of neutrons  =

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

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.