There are 4 things that are evidence of a chemical change.
1)Change in color
2)Change in shape (gas being let out)
3)Change in temperature
4)Change in smell
Burning wood is a chemical change because it has a change in color, and shape.
<span>Answer: 100 ml
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<span>Explanation:
1) Convert 1.38 g of Fe₂S₃ into number of moles, n
</span>i) Formula: n = mass in grass / molar mass
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ii) molar mass of </span><span>Fe₂S₃ =2 x 55.8 g/mol + 3 x 32.1 g/mol = 207.9 g/mol
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iii) n = 1.38 g / 207.9 g/mol = 0.00664 moles of <span>Fe₂S₃
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<span>2) Use the percent yield to calculate the theoretical amount:
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<span>65% = 0.65 = actual yield/ theoretical yield =>
</span>theoretical yield = actual yield / 0.65 = 0.00664 moles / 0.65 = 0.010 mol <span>Fe₂S₃</span><span>
3) Chemical equation:
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<span> 3 Na₂S(aq) + 2 FeCl₃(aq) → Fe₂S₃(s) + 6 NaCl(aq)
4) Stoichiometrical mole ratios:
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<span>3 mol Na₂S : 2 mol FeCl₃ : 1 mol Fe₂S₃ : 6 mol NaCl
5) Proportionality:
</span>2moles FeCl₃ / 1 mol Fe₂S₃ = x / 0.010 mol Fe₂S₃
<span>
=> x = 0.020 mol FeCl₃
6) convert 0.020 mol to volume
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<span>i) Molarity formula: M = n / V
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<span>ii) V = n / M = 0.020 mol / 0.2 M = 0.1 liter = 100 ml
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Answer:
- <u>1. Since the temperature of your body is higher than the temperature of the air and of the water, heat will flow from your body to the air and pool.</u>
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- <u>2. The pool feels cooler than air because the water can absorb heat energy faster than the air, due to liquids are better conductors than gases.</u>
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Explanation:
Heat always flows from warmer substances to colder ones.
The normal body temperature is 98ºF. Therefore, the heat will flow from your body to the air and pool, which are at a lower temperature of 80ºF. In both cases, you will lose thermal energy and the external parts of your body will cool down.
The difference between both cases is in the heat conduction capacity of both air and water.
Liquids (and solids) are better <em>thermal conductors </em>than gases because the conduction of heat occurs as result of the direct contact between the particles of matter: the atoms or molecules in hot matter vibrate faster than their neighbors and transmit them kinetic energy by direct contact.
Therefore, the liquid water in the swimming pool, at the same temperature than the air, will be able to absorb more heat in the same time from the body.
In conclusion, the body will cool down faster in water than in air which is why the pool feels cooler than air.
