Answer:
A. When a piece of copper is heated, it combines with oxygen to form copper oxide. The chemical reaction for the same is as follows:
2 Cu (s) + O2(g) => 2CuO
B. The mass of the piece of copper will remain same and there will be no change in its mass. However, its volume will increase, so its density will decrease.
C. This is so because heating copper in its elemental form is a physical change and there is no change in mass during a physical change. Hence, the mass of copper remain same.
I will solve this question assuming the reaction equation look like this:
<span>MnO2 + 4 HCl ---> MnCl2 + Cl2 + 2 H2O.
</span>
For every one molecule of MnO2 used, there will be one molecule of Cl2 formed. If the molecular mass of MnO2 is 87g/mol and molecular mass of Cl2 is <span> 73.0 g/mol, the mass of MnO2 needed would be:
Cl mass/Cl molecular mass * MnO2 molecular mass=
25g/ (73g/mol) * (87g/mol) * 1/1= 29.8 grams</span>
Answer:
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Explanation:
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Mg(aq) + 2OH(aq) -> Mg(OH)2
Don't forget the charge of ions
Answer is: <span>c. 80 g of Br2.
</span>1) n(Li) = 14 g ÷ 7 g/mol
n(Li) = 2 mol.
N(Li) = 2 mol · 6·10²³ 1/mol.
N(Li) = 1,2·10²⁴.
2) n(He) = 4 g ÷ 4 g/mol.
n(He) = 1 mol.
N(He) = 1 mol · 6·10²³ 1/mol.
N(He) = 6·10²³.
3) n(Br₂) = 80 g ÷ 160 g/mol.
n(Br₂) = 0,5 mol.
N(Br₂) = 0,5 mol · 6·10²³ 1/mol.
N(Br₂) = 3·10²³.
4) n(H₂) = 4 g ÷ 2 g/mol = 2 mol.
N(H₂) = 1,2·10²⁴.