Answer:
c. 3
Explanation:
The unbalanced reaction expression is given as:
Fe + O₂ → Fe₂O₃
To balance the expression gives the coefficient of oxygen.
Assign the coefficients a,b, c and use a mathematical approach to solve this problem:
aFe + bO₂ → cFe₂O₃
Conserving Fe: a = 2c
O: 2b = 3c
Now let c = 1, a = 2, b = 
Multiply through by 2,
a = 4, b = 3 and c = 2
4Fe + 3O₂ → 2Fe₂O₃
The coefficient of O₂ is 3
The formula that can be applied in this problem is W = Fd
where W is work, F is the force and d is distance. You have 450N and 3m, all
you have to do is to multiply it.
W = Fd
W = (450N) (3m)
W = 1350J
The answer is letter C.
<span>1. What is the colour of FeSO4.7H20 crystals?How does this colour change upon heating?
</span><span>Melanterite or FeSO4.7H20 is green in color
</span>2FeSO4 ---> Fe2O3 + SO2 + SO3<span>
2. a. What are redox reactions?
It </span><span>is a type of chemical </span>reaction<span> that involves a transfer of electrons between two species.
</span><span>
b.Why is the reaction between MnO2 and HCl a
redox reaction?
Because there are atoms that are reduced and are oxidized.
c.Identify the substance oxidized and the
substance reduced in the above reaction.
</span>MnO2<span> + 4 </span>HCl<span> ---> MnCl2 + 2H2O + Cl2
</span>Mn was reduced and Cl was oxidized
Answer: option <span>D Chemical reaction rates vary with the conditions of the reaction, but nuclear decay rates do not.
Justification:
1) The rate of chemical reactions are affected by: concentration of the reactants, state of the reactants, temperature, and presence of catalizers. So the first part of the statement is true.
2) Nuclear decay rates are constant. The decay depends on the nature of the element but not the conditions. That is why dating fossils with radiactive isotopes is possible. So, the second part of the statement is true.
</span>
Missing question:
Chemical reaction: H₂ <span>+ 2ICl → 2HCl + I</span>₂.
t₁ = 5 s.
t₂ = 15 s.
c₁ = 1,11 M = 1,11 mol/L.
c₂ = 1,83 mol/L.
rate of formation = Δc ÷ Δt.
rate of formation = (c₂ - c₁) ÷ (t₂ - t₁).
rate of formation = (1,83 mol/L - 1,11 mol/L) ÷ (15 s - 5 s).
rate of formation = 0,72 mol/L ÷ 10 s.
rate of formation = 0,072 mol/L·s.
