Answer:
a star shines due to thermonuclear fusion
Explanation:
Answer : 0.8663 Kg of chalcopyrite must be mined to obtained 300 g of pure Cu.
Solution : Given,
Mass of Cu = 300 g
Molar mass of Cu = 63.546 g/mole
Molar mass of 
= 183.511 g/mole
- First we have to calculate the moles of Cu.
The moles of Cu = 4.7209 moles
From the given chemical formula, we conclude that the each mole of compound contain one mole of Cu.
So, The moles of Cu = Moles of = 4.4209 moles
- Now we have to calculate the mass of .
Mass of = Moles of × Molar mass of = 4.4209 moles × 183.511 g/mole = 866.337 g
Mass of = 866.337 g = 0.8663 Kg (1 Kg = 1000 g)
Therefore, 0.8663 Kg of chalcopyrite must be mined to obtained 300 g of pure Cu.
Answer:
radiation and conduction
Explanation:
During a warm summer day, a car became extremely hot. When a student went to open the car door, he burned his fingers. What two forms of energy were responsible for the student burning his fingers?
Solution:
Heat is the transfer of energy from a warmer object to a cooler object. For heat transfer to occur, there have to be a difference in temperature between two objects.
Heat can be transferred in three ways: by conduction, by convection, and by radiation.
Conduction is the transfer of thermal energy between bodies through direct contact. Convection is the transfer of thermal energy through the movement of heat in a liquid or gas. Radiation is the transfer of thermal energy through thermal emission by electromagnetic waves.
During a warm summer day, The sun makes the car to become hot through energy transfer from the sun to the car. When the student touch the car, there is heat transfer as a result of conduction.
Answer: 1 molar NaOH contains 40 grams of NaOH per every liter of water
Explanation:
so 2 M NaOH contains twice that amount, ie. 80 grams per liter. Then, ine 250 ml of weater, there should be 80/4 = 20 grams of solid NaOH dissolved.
Answer:
36.55kJ/mol
Explanation:
The heat of solution is the change in heat when the KNO3 dissolves in water:
KNO3(aq) → K+(aq) + NO3-(aq)
As the temperature decreases, the reaction is endothermic and the molar heat of solution is positive.
To solve the molar heat we need to find the moles of KNO3 dissolved and the change in heat as follows:
<em>Moles KNO3 -Molar mass: 101.1032g/mol-</em>
10.6g * (1mol/101.1032g) = 0.1048 moles KNO3
<em>Change in heat:</em>
q = m*S*ΔT
<em>Where q is heat in J,</em>
<em>m is the mass of the solution: 10.6g + 251.0g = 261.6g</em>
S is specififc heat of solution: 4.184J/g°C -Assuming is the same than pure water-
And ΔT is change in temperature: 25°C - 21.5°C = 3.5°C
q = 261.6g*4.184J/g°C*3.5°C
q = 3830.87J
<em>Molar heat of solution:</em>
3830.87J/0.1048 moles KNO3 =
36554J/mol =
<h3>36.55kJ/mol</h3>
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