Answer:
11
Explanation:
Data obtained from the question include:
Mass number = 23
Neutron = 12
Atomic number =.?
Next, we shall determine the number of protons present in the element.
This can be achieved by doing the following:
Mass number = Proton + Neutron
Mass number = 23
Neutron = 12
Proton =...?
Mass number = Proton + Neutron
23 = Proton + 12
Collect like terms
Proton = 23 – 12
Proton = 11
The atomic number of an element is equal to the proton number.
Atomic number = proton number
Proton number = 11
Atomic number = proton = 11
Therefore, the atomic number is 11.
0.0340 g O2
<em>Step 1.</em> Write the balanced chemical equation
4Fe(OH)^(+) + 4OH^(-) + O2 + 2H2O → 4Fe(OH)3
<em>Step 2</em>. Calculate the moles of Fe^(2+)
Moles of Fe^(2+) = 50.0 mL Fe^(2+) × [0.0850 mmol Fe^(2+)/1 mL Fe^(2+)]
= 4.250 mmol Fe^(2+)
<em>Step 3</em>. Calculate the moles of O2
Moles of O2 = 4.250 mmol Fe^(2+) × [1 mmol O2/4 mmol Fe^(2+)]
= 1.062 mmol O2
<em>Step 4</em>. Calculate the mass of O2
Mass of O2 = 1.062 mmol O2 × (32.00 mg O2/1 mmol O2) = 34.0 mg O2
= 0.0340 g O2
It is in a large elliptical shape!
A "natural" chemical change would be burning wood, cooking eggs, baking a cake and milk going sour. These changes can't be changed so therefore they are chemical changes.
A natural physical change would be mixing salt or sand with water, melting or boiling water, cutting wood, and shredding paper. The salt and sand can be removed from the water. Hot and cold water are still water. Wood and paper didn't change their composition. All of these examples are reversible.
