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Tom [10]
3 years ago
7

A corpse discovered in the desert at 5:00 PM was found to have larvae from the blow fly species Phormia regina that had just dev

eloped into the first instar stage. Controlled experiments show that this species requires 16.0 hours at 26.7 ∘ C to develop from an egg to the first instar stage. The average nighttime temperature in the desert was 22.4 ∘ C , and the average daytime temperature was 37.8 ∘ C . If the sunset occurred at 9:00 PM and the sunrise occurred at 7:00 AM, how many hours prior to discovery was the corpse placed in the desert?
Chemistry
1 answer:
horrorfan [7]3 years ago
3 0

Answer:

12.19 hours prior to discovery was the corpse placed in the desert.

Explanation:

Heat required for fly eggs to develop into first instar larvae = Exposure\,time\times temperature

From the given,

Exposure time = 16 hrs

Temperature = 27 C

=16\times 27 = 427.2^{o}C

The day time exposed hours is 10 hrs.-(7.00am-5.00pm)

=10\times 37.8 = 378^{o}C

So, the extra heat  = 427.2-378= 49.2

The addition heat divided by average temperature.

Average temperature = 22.4 C

=\frac{49.2}{22.4}= 2.19 hrs

So, the total time exposed is night time hours to day time hours.

= 10+2.19 = 12.19 hrs.

Therefore, 12.19 hours prior to discovery was the corpse placed in the desert.

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The oxidation of Cu₂O(s) to CuO(s) is an exothermic process:
Alex73 [517]

Answer:

w = 7376.6 J

Explanation:

To calculate the work done in the system, we need first to calculate the number of moles of all compounds.

The following expression, that comes from the 1° law of thermodynamic, will help you to get the work:

w = ΔnRT

Where:

Δn: difference in the number of moles between products and reactants

R: constant universal of gases (8.314 J / mol K)

T: Temperature in Kelvin.

As we are doing this reaction in STP, then the Pressure is 1 atm, and temperature is 0 °C or 273 K.

Now, we already have the moles of Cu₂O, let's see, according to the balanced reaction, how many moles we should have of O₂ and CuO.

If 1 mole of O₂ reacts with 2 moles of Cu₂O then 6.5 moles of Cu₂O will be:

moles O₂ = 6.5 moles Cu₂O * (1 mole O₂/2 moles Cu₂O) = 3.25 moles O₂

If 2 moles of Cu₂O produces 4 moles of CuO, then 6.5 moles will be:

moles CuO = 6.5 moles Cu₂O*(4 moles CuO/2 moles Cu₂O) = 13 moles CuO

Now that we have the moles, let's calculate the value of Δn.

Δn = moles product - moles reactants

Δn = 13 - (6.5 + 3.25) = 3.25 moles

Now, we can calculate the work done in the system:

w = 3.25 * (8.314 * 273)

<h2>w = 7376.6 J or 7.3766 kJ</h2>

Hope this helps

8 0
3 years ago
80 POINTS!! Will mark brainliest if answer is correct with all work shown.
Stella [2.4K]

Answer:

536 grams

The balanced equation is Ba + 2 HBr ==> BaBr2 + H2, so that indicates that mole of Ba will react with 2 moles of HBr. So let's determine how many moles of HBr we have and from there, determine the number of moles of Ba needed and the mass of that much Ba. The number of moles of HBr is simply the product of volume of solution used and its molarity. So:

1.30 L * 6.00 mol/L = 7.80 mol

And since we only need half as many moles of Ba, 7.80 mol / 2 = 3.90 mol of Ba is needed. The atomic weight of Ba is 137.327 g/mol. So the mass needed is 137.327 g/mol * 3.90 mol = 535.5753 g.

Rounding to 3 significant figures gives 536 grams.

8 0
3 years ago
Calculate the mass in amu of 75 atoms of aluminum
lyudmila [28]
<span>Calculating mass using Atomic Mass Units (amu):. Ex. Calculate the mass, in amu, of a sample of aluminum that contains 75 atoms. 1 Al atom = 26.98 amu.</span>
4 0
3 years ago
How many moles are in 89 grams of KCI
Pani-rosa [81]

Answer:

The number of moles in 89 grams of KCl is approximately 1.193 moles

Explanation:

A mole of an element or compound, is the quantity of the element or compound that contains 6.022 × 10²³ molecules of the element or compound, such that the molar mass of one mole is dependent on the mass of each molecule of the element or compound that make up the 6.022 × 10²³ particles

The given parameters are;

The mass of the KCl = 89 grams

The Molar mass, MW, of potassium, K = 39.1 g/mole

The Molar mass, MW, of chlorine, Cl = 35.5 g/mole

Therefore, given that KCl, has one K and one Cl, per mole, we have;

The Molar mass, MW, of potassium chloride, KCl = (39.1 + 35.5) g/mole = 74.6 g/mole

The \ number \ of \ moles, n=\dfrac{Mass}{Molar \ mass, MW}

Therefore, the number of moles of KCl in 89 g, 'n' is given as follows;

n = (89 g)/(74.6 g/mole) ≈ 1.193 moles

The number of moles in 89 grams of KCl, n ≈ 1.193 moles.

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Answer:

Poop

Explanation:

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