<span>Answer:
For this problem, you would need to know the specific heat of water, that is, the amount of energy required to raise the temperature of 1 g of water by 1 degree C. The formula is q = c X m X delta T, where q is the specific heat of water, m is the mass and delta T is the change in temperature. If we look up the specific heat of water, we find it is 4.184 J/(g X degree C). The temperature of the water went up 20 degrees.
4.184 x 713 x 20.0 = 59700 J to 3 significant digits, or 59.7 kJ.
Now, that is the energy to form B2O3 from 1 gram of boron. If we want kJ/mole, we need to do a little more work.
To find the number of moles of Boron contained in 1 gram, we need to know the gram atomic mass of Boron, which is 10.811. Dividing 1 gram of boron by 10.811 gives us .0925 moles of boron. Since it takes 2 moles of boron to make 1 mole B2O3, we would divide the number of moles of boron by two to get the number of moles of B2O3.
.0925/2 = .0462 moles...so you would divide the energy in KJ by the number of moles to get KJ/mole. 59.7/.0462 = 1290 KJ/mole.</span>
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Answer:
chyba się zniszczy
Explanation:
ponieważ sie film prześwietli
Answer:
C. 2.70 g/mL
Explanation:
Density is the ratio between the mass of a substance and the volume it occupies. Based on Archimedes' volume, the displaced volume of the aluminium is the volume it occupies. To solve this question we must find the difference in volume between initial volume of water = 30mL and final volume of water + aluminium = 39.26mL. This difference is the volume of the aluminium. With its mass we can find density:
39.26mL - 30mL = 9.26mL
Density = 25.00g / 9.26mL =
2.70g/mL
Right answer is:
<h3>C. 2.70 g/mL
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