Answer:
the answers are b, c, e, h, and j
Explanation:
There are four type of crystals possible in solids state , given as follows -
1. Ionic crystals -
In this type of crystals ionic bond is involved for the bonding between two atoms , which connects two oppositely charged atoms , i.e. , cation and anion together .
The ionic crystal from the given options are -
(d) KBr and (g) LiCl .
2. Covalent crystals -
The bond formed in these type of crystals are from share the electrons , i.e. making a covalent bond .
Hence ,
From the given options , the covalent crystals are -
(b) B₁₂ and (f) SiO₂ .
3. Molecular crystals -
weak intermolecular forces , like the dispersion forces , holds the atoms together , generating a molecular crystal .
Hence ,
From the given options , the molecular crystals are -
(a) CO₂ and (c) S₈
4. Metallic crystal -
The type of bond , which make up a metallic crystal is , the metal cation with the delocalized electrons .
Hence ,
From the given options , the metallic crystals are -
(e) Mg and (h) Cr
Endothermic reactions absorb heat and exothermic reactions give off heat
A mixture of Cu2 and CuO of mass 8.828g is reduced to copper metal with hydrogen:
Cu2O + H2 --> 2Cu + H2O
CuO + H2 --> Cu + H2O
If the mass of pure copper isolated was 7.214g, determine the percent by mass of CuO in the original sample
Let x = grams of CuO in the original sample.
y = grams of Cu2O in the original sample.
Eq. #1 x + y = 8.828 grams
Molar mass of CuO = 63.5 + 16 = 79.5 grams
Moles of CuO = x ÷ 79.5
Molar mass of Cu2O = 63.546 + 32 = 95.5 grams
Moles of Cu2O = y ÷ 95.5
According to the 2nd balanced equation, CuO + H2 --> Cu + H2O ,
1 mole of CuO produces 1 mole of Cu.
So, x ÷ 79.5 moles of CuO will produce x ÷ 79.5 moles of Cu
According to the 1st balanced equation, Cu2O + H2 --> 2Cu + H2O,
1 mole of Cu2O produces 2 moles of Cu
So, (y ÷ 95.5) moles of Cu2O will produce 2 * (y ÷ 95.5) moles of Cu
Since, the mass of pure copper isolated was 7.214 grams
Moles of Cu = (7.214 ÷ 63.5)
Moles of Cu from Cu2O + moles of Cu from CuO = total moles of Cu!!
2 * (y ÷ 95.5) + (x ÷ 79.5) = (7.214 ÷ 63.5)
Multiply by both sides by 95.5 * 79.5 * 63.5 to get rid of denominators
(2 * 79.5 * 63.5) y + (95.5 * 63.5) x = (7.214 * 95.5 * 79.5)
10,096.5 y + 6,064.25 x = 36,418.0755
Divide both sides by 6,064.25
x + 1.665 y = 6
Eq.#2 x = 6 – 1.665 y
Eq. #1 x + y = 8.828
x = 8.828 – y
8.828 – y = 6 – 1.665 y
0.665 y = 2.828
y = 4.25 grams of Cu2O
x = 8.828 – 4.25 = 4.58 grams of CuO
% CuO = (4.58 ÷ 8.828) * 100 = 51.88% CuO
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