Answer:
719.83°C
Explanation:
The heat that the sample of Zinc gives is equal to the heat that water is absorbing. That is:
C(Zn) * m(Zn) * ΔT(Zn) = C(H2O) * m(H2O) * ΔT(H2O)
<em>Where:</em>
<em>C is specific heat (Zn: 0.390J/g°C; H2O: 4.184J/g°C)</em>
<em>m is mass (Zn: 2.50g; H2O: 65.0g)</em>
<em>ΔT (Zn: ?; H2O: (22.5°C - 20.0°C = 2.50°C)</em>
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Replacing:
0.390J/g°C * 2.50g * ΔT(Zn) = 4.184J/g°C * 65.0g * 2.50
ΔT(Zn) = 697.33°C
As final temperature of Zn is 22.50°C, initial temperature is:
Initial temperature: 697.33°C + 22.50°C
719.83°C
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This is an acid base reaction and the chemical equation for the above reaction is as follows;
KOH + HClO₄ ---> KClO₄ + H₂O
the stoichiometry of acid to base is 1:1
KOH is a strong base and HClO₄ is a strong acid therefore they both ionize completely into their respective ions
Number of KOH moles - 0.723 M/1000 mL/L x 25.0 mL = 0.018 mol
Number of HClO₄ moles - 0.273 M/1000 mL/L x 50 mL = 0.013 mol
since acid and base react completely, 0.013 mol of acid reacts with 0.013 mol of base.
The excess base remaining is - 0.018 - 0.013 = 0.005 mol
total volume of solution = 25.0 mL + 50.0 mL = 75.0 mL
[OH⁻] = 0.005 mol/0.075 L = 0.067 M
pOH = -log[OH⁻]
pOH = -log(0.067 M)
pOH = 1.17
pOH + pH = 14
Therefore pH = 14 - 1.17 = 12.83
by knowing pH we can calculate the [H₃O⁺]
pH = -log [H₃O⁺]
[H₃O⁺] = antilog[-12.83]
[H₃O⁺]= 1.47 x 10⁻¹³ M
B. A chemical change has occurred and energy was given off
There are many kinds of pyroclastic material ejected during a volcanic eruption. Ash is the most common pyroclastic rock material ejected during an eruption. Volcanic ash is so fine that it can be blown into the atmosphere and picked up by the jet stream where it can circle the Earth for several years.
B. The unknown solution had the lower concentration.
Explanation:
Osmosis is a phenomenon in which the molecules of the solvent has a tendency to move through a membrane which is semipermeable from lower concentrated side to the higher concentration side, so that the concentrations on both sides of the membrane must be equal.
So the unknown solution may have lesser concentration than the isotonic solution so that molecules of that solution move from less concentrated side to the more concentrated side, so its level drops.
