4. A
because PbCl2 is an ionic compound and it's solid, so it's a substance.
It cannot be mixture, because it's a pure molecule.
5. D
despite that both substances are gases, colorless they are different molecules, so they should have different either chemical and physical properties
6. C
this substance made from W atoms and others are made from molecules
A bright feild is most commonly used
Answer:
D
Explanation:
Gibb's free energy change(∆G) and Standard electrode potential of electrochemical (Ecell) determine the spontaneity of a reaction.
when ∆G > 0, the reaction is not spontaneous
∆G < 0, the reaction is spontaneous
∆G = 0, the reaction is in equilibrium
when Ecell > 0, the redox reaction is spontaneous
Ecell < 0, the redox reaction is not spontaneous
Ecell = 0, the redox reaction is in equilibrium.
Answer is:<span>the yield is 50%.
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Chemical reaction: C + O₂ → CO₂.
n(C) = 0.3 mol; amount of substance.
n(O₂) = 0.3 mol.
From chemical reaction: n(C) : n(CO₂) = 1 : 1.
n(CO₂) = 0.3 mol.
M(CO₂) = 44 g/mol; molar mass of caron(IV) oxide.
m(CO₂) = n(CO₂) · M(CO₂).
m(CO₂) =0.3 mol · 44 g/mol.
m(CO₂) = 13.2 g; mass of carbon(IV) oxide.
the yield = 6.6 g ÷ 13.2 g · 100%.
the yield = 50%.
