A food provides enough energy to raise the temperature of 2000 grams of water by 10°c contains 20 KCa.
1 Calorie is the amount of heat needed to elevate one gram of water to one degree Celsius temperature at one atmosphere of pressure.
The term "kilocalorie" is used to describe the amount of energy needed to increase 1 L of water's temperature by one degree Celsius at sea level.
Given
Mass of water (m) = 2000 g
Temp raise (ΔT) = 10°C
Heat capacity of water (C) = 1 calorie/g-C
Formula used
Heat (ΔH) = m × C × ΔT
= 2000 × 10 = 20000 C
In Kilo calories
20000 C = 20000/1000 = 20 KCa
Hence, a food provides enough energy to raise the temperature of 2000 grams of water by 10°c contains 20 KCa.
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Answer:
A. increasing the ability of technology, like microscopes, to see even smaller particles
a) The reaction is exothermic since the overall enthalpy change is negative. this means that the system has lost energy to the environment, namely, the apparatus and due to drought.
b) We first calculate the number of moles in 3.55 grams of magnesium.
number of moles= mass/ atomic mass
=3.55/24
=0.1479 moles(to 4sf)
now, if 2 moles of magnesium give -1204kJ
How much energy is given by 0.1479 moles
= (0.1479×-1204kJ)
=-89.0358kJ (don't forget the negative sign)
c) two molesof MgO produces -1204kJ of energy
then -234kJ will be produced by
=(-234kJ×2moles)/1204kJ
=0.3887moles
one mole of MgO weighs 24+16=40
therefore the mass produced is 0.3887moles×40=15.548grams
(d) we first find the number of moles of MgO in 40.3 grams
number of moles=mass/RFM
=40.3g/40= 1.0075moles
if 2 moles of MgO give 1204 kJ then decomposing 1.0075 moles requires
(1.0075 moles×1204kJ)/2=606.515kJ
