Match each event with its discription

A freezer compartment is covered with a 2-mm-thick layer of frost at the time it malfunctions. If the compartment is in ambient

ruslelena [56]

Answer:

The time required to melt the frost is 3.25 hours.

Explanation:

The time required to melt the frost dependes on the latent heat of the frost and the amount of heat it is transfered by convection to the air .

The heat transferred per unit area can be expressed as:

$q=h_c*A*\Delta T\\\\q/A=h_c*\Delta T$

being hc the convective heat transfer coefficient (2 Wm^-2K^-1) and ΔT the difference of temperature (20-0=20 °C or K).

$q/A=h_c*\Delta T=2\frac{W}{m^2K}*20K=40\frac{W}{m^2}$

If we take 1 m^2 of ice, with 2 mm of thickness, we have this volume

$V=T*A = 0.002 m * 1 m^2=0.002m^3$

The mass of the frost can be estimated as

$M=\rho * V=700\frac{kg}{m^3}*0.002m^3= 1.4 kg$

Then, the amount of heat needed to melt this surface (1 m²) of frost is

$Q=L*M=334\frac{kJ}{kg}*1.4kg= 467.6kJ$

The time needed to melt the frost can be calculated as

$t=\frac{Q}{(q/A)}=\frac{467.6kJ/m2}{40W/m2} = 11.69\frac{kJ}{W}*\frac{1W*s}{1J}*\frac{1000J}{1kJ}= 11690s=3.25h$

7 0

3 years ago

Which event would be impossible to explain by using John Dalton’s model of the atom?

geniusboy [140]

The scientist thought that the atom was the smallest particle in the universe is John Dalton. He established the atomic theory which consists of five; elements are made of extremely small particles called atoms, atoms of different element have different sizes, mass and physic – chemical properties, atoms cannot be divided further, destroyed or created, atoms can combine to form compounds and in chemical reaction, atoms can be combined, separated or rearranged.

5 0

4 years ago

Read 2 more answers

Using the van der Waals equation, the pressure in a 22.4 L vessel containing 1.00 mol of neon gas at 100 °C is ________ atm. (a

svetoff [14.1K]

Answer:

The answer to your question is P = 1.357 atm

Explanation:

Data

Volume = 22.4 L

1 mol

temperature = 100°C

a = 0.211 L² atm

b = 0.0171 L/mol

R = 0.082 atmL/mol°K

Convert temperature to °K

Temperature = 100 + 273

= 373°K

Formula

$(P + \frac{a}{v^{2}} )(v - b) = RT$

Substitution

$(P + \frac{0.211}{22.4})(22.4 - 0.0171) = (0.082)(373)$

Simplify

(P + 0.0094)(22.3829) = 30.586

Solve for P

P + 0.0094 = $\frac{30.586}{22.3829}$

P + 0.0094 = 1.366

P = 1.336 - 0.0094

P = 1.357 atm

7 0

4 years ago

The aldol reaction is catalyzed by acid as well as base. What is the reactive nucleophile in the acid-catalyzed aldol reaction

svp [43]

Answer:

The reactive nucleophile is Ketone.

Explanation:

In organic chemistry, The process of acid - catalyzed aldol condensation starts from when ketone (or any aldehyde) is converted to an -enol, after which it attacks another ketone/aldehyde that has already been activated by parbonyl oxygen protonation.

The process of this is that first of all the ketone undergoes tautomerization to form -enol. Thereafter, the other carbonyl will undergo protonation which makes the carbon activated towards attack. Now, the nucleophilic enol will be added to the carbonyl in a [1,2]-addition reaction and we will now use deprotonation to obtain the neutral Aldol product.

Now, since only the ketone can produce an -enol, thus it is the nucleophile as aldehydes are better electrophiles

4 0

3 years ago

What is missing from the temperature and volume graph shown at right?

Kaylis [27]

Answer: Three things are missing:

i) Graph title.

ii) Label for the vertical axis.

iii) The scale and the units for the horizontal axis.

Justification:

1) Find the graph in the image attached.

2) What does the graph represent? You cannot tell because it does not show the tittle.

Since you are told in the statement that it is a temperature and volume graph, the appropiate title would be:

Temperature vs. Volume.

3) The vertical axis also must be properly labeled, including the units.

A good label for the vertical axis of this graph might be: Volume (cm³). It migh also be liters, gallons, or other volume unit.

4) Although the horizontal axis is labeled, it does not indicate the units and the scale. So, you know neither if the temperature shown is celsius, (°C), farenheti (°F), kelvin (K), or rankine (R) (those are the four major scales of temperature), nor how much each division represent (1, 5, 10, 10, 50, 100?)

4 0

4 years ago