Answer:
B. The temperature of the water when the food sample has finished burning completely.
Explanation:
Heat or thermal energy is a form of energy that transfers from one object to another due to a temperature difference between the objects. The units for heat are joules or calories.
Calorimetry is the measurement of heat energy released or absorbed in a chemical reaction. A calorimeter is used in calorimetry. The calorimeter operates on the Law of Conservation of Energy which states that energy is never created or destroyed but is transformed from one form to another or between objects.
In food calorimetry, the energy released when food is burned is measured by recording the rise in temperature of water in a calorimeter when a given mass of a food sample is burned completely.
Energy can be calculated using the formula: Q = mc ∆T
where Q = the energy in joules or calories, m = the mass in grams, c = specific heat and ∆T = the change in temperature (final temperature - initial temperature).
The temperature of the water when the food sample has finished burning completely is taken as the final temperature of the water. The sample is allowed to smolder for sometime before recording the final water temperature. This is because the water temperature will continue to rise after the flame has gone out.
Answer:
25000 ppm
Explanation:
<em>Parts Per Million </em>is defined as the number of parts of a solute per one million parts of a solution.
ppm = (Weight of Solute / Weight of Solution) × 10⁶ ---(1)
Let us suppose that the air (solution) weights 100 grams, then 2.5 % of water vapors will have following mass,
Mass of Vapors g / 100 g × 100 = 2.5
Or,
Mass of Vapors = 2.5 × 100 / 100
Mass of Vapors = 2.5 g
Hence, mass of water vapors is 2.5 g.
Now, putting mass of water vapors and air in eq. 1,
ppm = (2.5 / 100) × 10⁶
ppm = 25000
Answer:
6
Explanation:
As , 2H2 + O2 = 2H2O
with 6 H2, 4O2 is excess.
H2O molecules formed = 6
<span>The energy (E) per photon is expressed by Planck's equation: E = hf, where f is
the frequency and h is Planck's constant, experimentally determined to be
6.625 * 10**-34 joule-seconds. So to find E, we multiply h by the frequency
and obtain E = hf = (6.625 * 10**-34)(7.0 * 10**14) = 46.375 * 10**-20 joule
or in standard notation, E = 4.6375 * 10**-19 joule per photon.
Hope this answers your question.Sorry if I calculated wrong.</span>
Answer:
The limiting reactant is H₂
Explanation:
The reaction of hydrogen (H₂) and carbon monoxide (CO) to produce methanol (CH₃OH) is the following:
2H₂(g) + CO(g) → CH₃OH(g)
From the balanced chemical equation, we can see that 1 mol of CO reacts wIth 2 moles of H₂. So, the stoichiometric ratio is:
2 mol H₂/1 mol CO = 2.0
We have 500 mol of CO and 750 mol of H₂, so we calculate the ratio to establish a comparison:
750 mol H₂/500 mol CO = 1.5
Since 2.0 > 1.5, we have fewer moles of H₂ than are needed to completely react with 500 moles of CO. In fact, we need 1000 moles of H₂ and we have 750 moles. So, the limiting reactant is H₂.
