The balanced equation for the reaction is as follows;
Ca(OH)₂ + 2HBr --> CaBr₂ + 2H₂O
stoichiometry of Ca(OH)₂ to HBr is 1:2
number of Ca(OH)₂ moles reacted - 0.10 mol/L x 0.1000 L = 0.010 mol
Number of HBr moles added - 0.10 mol/L x 0.4000 = 0.040 mol
1 mol of Ca(OH)₂ needs 2 mol of HBr for neutralisation
therefore 0.010 mol of Ca(OH)₂ needs - 0.010 x 2 = 0.020 mol of HBr to be neutralised
but 0.040 mol of HBr has been added therefore number of moles of HBr in excess - 0.040 - 0.020 = 0.020 mol
then pH of the medium can be calculated using the excess H⁺ ions
HBr is a strong acid therefore complete ionization
[HBr] = [H⁺]
[H⁺] = 0.020 mol / (100.0 + 400.0 mL)
= 0.020 mol / 0.5 L
= 0.040 mol/L
pH = -log[H⁺]
pH = - log [0.040 M]
pH = 1.40
pH of the medium is 1.40
The way you calculate the empirical formula is to firstly assume 100g. To find each elements moles you take each elements percentage listed, times it by one mole and divide it by its atomic mass. (ex: moles of K =55.3g x 1 mole/39.1g, therefore there is 1.41432225 moles of Potassium) Once you’ve completed this for every element you list each elements symbol beside it’s number of moles and divide by the smallest number because it can only go into its self once. After you’ve done this, you’ve found your empirical formula, which is the simplest whole number ratio of atoms in a compound. I’ve added an example of a empirical question I completed last semester :)
<u>Answer:</u> The uncertainty in the velocity of oxygen molecule is 
<u>Explanation:</u>
The diameter of the molecule will be equal to the uncertainty in position.
The equation representing Heisenberg's uncertainty principle follows:
where,
= uncertainty in position = d = 
= uncertainty in momentum = 
m = mass of oxygen molecule = 
h = Planck's constant = 
Putting values in above equation, we get:
Hence, the uncertainty in the velocity of oxygen molecule is
In an atom, the number of neutrons determines most specifically the isotopes of an element.
<h2>Further Explanation</h2><h3>An atom </h3>
- An atom is defined as the smallest particle of an element that can take part in a chemical reaction.
- Atoms are made of energy shells and the inner nucleus.
- It is also made up of subatomic particles, protons and neutrons.
<h3>Neutrons </h3>
- They are sub-atomic particles in an atom that are found in the nucleus of an atom. They have a zero charge or no charge.
- Neutrons are slightly heavier than protons.
- The number of protons and neutrons in a nucleus of an atom results to the atomic mass number of an atom. Like protons they only take part in nuclear reactions.
<h3>Protons</h3>
- Protons are subatomic particles that are found in the nucleus of an atom. They are positively charged. with a charge of +1.
- The number of protons differ from one element to another and thus used as the atomic number of an individual element.
- The nucleus of an atom is positively charged due to the positive charge of the protons.
- Additionally, protons do not take part in chemical reactions but in nuclear reactions.
<h3>Electrons </h3>
- They are found orbiting the nucleus on energy shells based on Clouds’ theory. Electrons are negatively charged each with a charge of -1.
- The number of electrons and protons in a neutral atom are equal. Additionally they have the least mass of the three sub-atomic particles.
- Electrons are the only sub-atomic particles that take part in chemical reactions.
<h3>Isotopes </h3>
- Isotopes are atoms of the same element that have the same mass number but different atomic number.
<h3>Mass number;</h3>
- Mass number is the sum of the number of protons and neutrons in the nucleus of an atom of an element.
Keywords: Atom, sub-atomic particles, electrons, protons, neutrons, isotopes
<h3>Learn more about:</h3>
Level: High school
Subject: Chemistry
Topic: Atomic structure
Answer:
6.32 moles of Fe
Explanation:
The given chemical equation is presented as follows;
2Fe + 3Cl₂ → 2FeCl₃
The mass of Cl₂ in the reaction = 336 grams
The molar mass of chlorine gas Cl₂ = 35.435 g/mol
The number of moles, n = Mass/(Molar mass)
The number of moles of Cl₂ in the reaction, n = 336 g/(35.435 g/mol) ≈ 9.842 moles
From the given reaction, 3 moles of Cl₂ react with 2 moles of Fe to produce 2 moles of FeCl₃
By the law of definite proportions, we have that 9.482 moles of Cl₂ will react with approximately 9.482 × 2/3 = 6.32 moles of Fe to produce approximately 6.32 moles of FeCl₃
Therefore, approximately 6.32 moles of Fe will be required to react with 336 grams of Cl₂.
