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2 years ago

On average, how many hours of sleep do teenagers need each night? 7 hours 7.5 hours 8 hours 8.5 hours

Chemistry

2 answers:

Marrrta [24]2 years ago

5 0

Answer:

8 to 8.5 since that is the recommended and people usualy sleep more than that

Vera_Pavlovna [14]2 years ago

3 0

Answer:

7.5

Explanation:

i listened to the other dude and got it wrong but it showed this answer to be correct

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Phoebe removes frozen vegetables from the freezer to make herself a stir-fry. She’s in a bit of a hurry, so she immerses the pla

Alexxandr [17]

This is thermal conduction.
In conduction area with higher kinetic energy (in this case how water) transfer thermal energy to an area with lower kinetic energy (in this case frozen vegetables). Thermal c<span>onduction takes place in all phases of </span>matter (solids, liquids, gases). Rate of conduction is proportional with <span>temperature difference between substances.</span>

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3 years ago

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Nata [24]

Answer:

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2 years ago

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When a student mixes 50 mL of 1.0 M HCl and 50 mL of 1.0 M NaOH in a coffee-cup calorimeter, the temperature of the resultant so

zmey [24]

Answer: 54.4 kJ/mol

Explanation:

First we have to calculate the moles of HCl and NaOH.

$\text{Moles of HCl}=\text{Concentration of HCl}\times \text{Volume of solution}=1.0M\times 0.05=0.05mole$

$\text{Moles of NaOH}=\text{Concentration of NaOH}\times \text{Volume of solution}=1.0\times 0.05L=0.05mole$

The balanced chemical reaction will be,

$HCl+NaOH\rightarrow NaCl+H_2O$

From the balanced reaction we conclude that,

As, 1 mole of HCl neutralizes by 1 mole of NaOH

So, 0.05 mole of HCl neutralizes by 0.05 mole of NaOH

Thus, the number of neutralized moles = 0.05 mole

Now we have to calculate the mass of water:

As we know that the density of water is 1 g/ml. So, the mass of water will be:

The volume of water = $50ml+50ml=100ml$

$\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1g/ml\times 100ml=100g$

Now we have to calculate the heat absorbed during the reaction.

$q=m\times c\times (T_{final}-T_{initial})$

where,

q = heat absorbed = ?

$c$ = specific heat of water = $4.18J/g^oC$

m = mass of water = 100 g

$T_{final}$ = final temperature of water = $27.5^0C$

$T_{initial}$ = initial temperature of metal = $21.0^0C$

Now put all the given values in the above formula, we get:

$q=100g\times 4.18J/g^oC\times (27.5-21.0)^0C$

$q=2719.6J=2.72kJ$

Thus, the heat released during the neutralization = 2.72 KJ

Now we have to calculate the enthalpy of neutralization per mole of $HCl$ :

0.05 moles of $HCl$ releases heat = 2.72 KJ

1 mole of $HCl$ releases heat = $\frac{2.72}{0.05}\times 1=54.4KJ$

Thus the enthalpy change for the reaction in kJ per mol of HCl is 54.4 kJ

6 0

2 years ago

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What is the theoretical yield of moles of hydrogen that can be produced from 0.032g of MG?

Ugo [173]

Answer:

1.31x10⁻³ moles of H₂

Explanation:

This is the equation:

Mg(s) + 2H₂O (g) → Mg(OH)₂ (aq) + H₂(g)

Ratio is 1:1, so 1 mol of Mg is needed to produce 1 mol of H₂

Mass / Molar mass = Mol

0.032 g / 24.3 g/m = 1.31x10⁻³ moles

1.31x10⁻³ moles of H₂(g)

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2 years ago

Why are fibers birefringent

horrorfan [7]

Inevitable manufacturing imperfections in optical fiber leads to birefringence, which is one cause of pulse broadening in fiber-optic communications. Such imperfections can be geometrical (lack of circular symmetry), due to stress applied to the optical fiber and/or due to bending of the fiber.

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2 years ago

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