6. How many moles of water would require 92.048 kJ of heat to raise its temperature from 34.0 °C to 100.0 °C? (3 marks)
1 answer:
Taking into account the definition of calorimetry, 0.0185 moles of water are required.
<h3>Calorimetry</h3>Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.
Sensible heat is defined as the amount of heat that a body absorbs or releases without any changes in its physical state (phase change).
So, the equation that allows to calculate heat exchanges is:
Q = c× m× ΔT
where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.
<h3>Mass of water required</h3>In this case, you know:
- Heat= 92.048 kJ
- Mass of water = ?
- Initial temperature of water= 34 ºC
- Final temperature of water= 100 ºC
- Specific heat of water = 4.186
Replacing in the expression to calculate heat exchanges:
92.048 kJ = 4.186 × m× (100 °C -34 °C)
92.048 kJ = 4.186 × m× 66 °C
m= 92.048 kJ ÷ (4.186 × 66 °C)
<u><em>m= 0.333 grams</em></u>
<h3>Moles of water required</h3>Being the molar mass of water 18 , that is, the amount of mass that a substance contains in one mole, the moles of water required can be calculated as:
<u><em>amount of moles= 0.0185 moles</em></u>
Finally, 0.0185 moles of water are required.
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Answer:
Explanation:
Molarity is found by dividing the moles of solute by liters of solution.
We are given grams of a compound and milliliters of solution, so we must make 2 conversions.
1. Gram to Moles
We must use the molar mass. First, use the Periodic Table to find the molar masses of the individual elements.
- C: 12.011 g/mol
- H: 1.008 g/mol
- O: 15.999 g/mol
Next, look at the formula and note the subscripts. This tells us the number of atoms in 1 molecule. We multiply the molar mass of each element by its subscript.
6(12.011)+12(1.008)+6(15.999)=180.156 g/mol
Use this number as a ratio.
Multiply by the given number of grams.
Flip the fraction and divide.
2. Milliliters to Liters
There are 1000 milliliters in 1 liter.
Multiply by 2500 mL.
3. Calculate Molarity
Finally, divide the moles by the liters.
The original measurement has 2 significant figures, so our answer must have the same. That is the hundredth place and the 3 tells us to leave the 7.
1 mole per liter is also equal to 1 M.