Answer:
d the amount of matter in a closed system is the same at the start of a reaction as at the end of the reaction
C) 10 grams
Explanation:
Potassium chlorate (KCIO₃) have a solubility in water at 70 °C of 30 grams in 100 grams of water.
If our solution have already 20 grams of potassium chlorate salt dissolved that means we need another 10 grams of potassium chlorate to reach the saturation point.
Learn more:
Potassium chlorate solubility in water
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So if you put a holo ball of paper in the water it sinks and as it sinks it gets smaller cuse pressure so it cuseus things to shrink cuse of pressure
0.042 moles of Hydrogen evolved
<h3>Further explanation</h3>
Given
I = 1.5 A
t = 1.5 hr = 5400 s
Required
Number of Hydrogen evolved
Solution
Electrolysis of water ⇒ decomposition reaction of water into Oxygen and Hydrogen gas.
Cathode(reduction-negative pole) : 2H₂O(l)+2e⁻ ⇒ H₂(g)+2OH⁻(aq)
Anode(oxidation-positive pole) : 2H₂O(l)⇒O₂(g)+4H⁻(aq)+4e⁻
Total reaction : 2H₂O(l)⇒2H₂(g)+O₂(g)
So at the cathode H₂ gas is produced
Faraday : 1 mole of electrons (e⁻) contains a charge of 96,500 C

Q = i.t
Q = 1.5 x 5400
Q = 8100 C
mol e⁻ = 8100 : 96500 = 0.084
From equation at cathode , mol ratio e⁻ : H₂ = 2 : 1, so mol H₂ = 0.042