Answer
Calculating the mass number for an atom requires that we know the atomic number and the number of protons in the atom’s nucleus. The mass number then gives us the average weight of atoms of a given element. However, as long as the number of protons equals the number of neutrons, the values balance out and we always obtain a whole number for the mass number.
Explanation:
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Explanation:
The balanced equation of the reaction is given as;
Mg(OH)2 (s) + 2 HBr (aq) → MgBr2 (aq) + 2 H2O (l)
1. How many grams of MgBr2 will be produced from 18.3 grams of HBr?
From the reaction;
2 mol of HBr produces 1 mol of MgBr2
Converting to masses using;
Mass = Number of moles * Molar mass
Molar mass of HBr = 80.91 g/mol
Molar mass of MgBr2 = 184.113 g/mol
This means;
(2 * 80.91 = 161.82g) of HBr produces (1 * 184.113 = 184.113g) MgBr2
18.3g would produce x
161.82 = 184.113
18.3 = x
x = (184.113 * 18.3 ) / 161.82 = 20.8 g
2. How many moles of H2O will be produced from 18.3 grams of HBr?
Converting the mass to mol;
Number of moles = Mass / Molar mass = 18.3 / 80.91 = 0.226 mol
From the reaction;
2 mol of HBr produces 2 mol of H2O
0.226 mol would produce x
2 =2
0.226 = x
x = 0.226 * 2 / 2 = 0.226 mol
3. How many grams of Mg(OH)2 are needed to completely react with 18.3 grams of HBr?
From the reaction;
2 mol of HBr reacts with 1 mol of Mg(OH)2
18.3g of HBr = 0.226 mol
2 = 1
0.226 = x
x = 0.226 * 1 /2
x = 0.113 mol
Answer:
Bakelite is a polymer made up of the monomers phenol and formaldehyde. This phenol-formaldehyde resin is a thermosetting polymer.
The correct matches for changes of state are:
- 1 or 3 : Arrow that shows particles getting closer together
- gas: State of matter that would fill any container
- liquid: State of matter with definite volume but NOT shape
- 2 or 4: Arrow that shows particles gaining energy
- solid: State of matter with definite shape
<h3>What is change of state?</h3>
Change of state is the process whereby matter in one physical state is converted to matter in another state by the addition or removal of heat.
The process of change of state are:
- Melting: solid to liquid due to addition of heat
- Vaporization: liquid to gas due to addition of heat
- Sublimation: solid to gas due to addition of heat
- Freezing: liquid to solid due to removal of heat
- Condensation: gas to liquid due to removal of heat
- Deposition: gas to solid due to removal of heat
Considering the given diagram, the correct matches are:
- 1 or 3 : Arrow that shows particles getting closer together
- gas: State of matter that would fill any container
- liquid: State of matter with definite volume but NOT shape
- 2 or 4: Arrow that shows particles gaining energy
- solid: State of matter with definite shape
In conclusion, change of state of matter occurs due to heat changes.
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