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Brilliant_brown [7]
3 years ago
7

The atomic number of magnesium is 12 this is also the number of which of the following

Chemistry
1 answer:
frozen [14]3 years ago
4 0
The atomic number represents the number of protons present in an atom.Therefore,the answer is B.
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How much energy in joules is released when 18.5 grams of copper cools from 285 °C<br> down to 45 °C
nadya68 [22]

Answer: 1709.4 Joules

Explanation:

The quantity of Heat Energy (Q) released on cooling a heated substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Since Q = ?

M = 18.5 grams

Recall that the specific heat capacity of copper C = 0.385 J/g.C

Φ = 285°C - 45°C = 240°C

Then, Q = MCΦ

Q = 18.5grams x 0.385 J/g.C x 240°C

Q = 1709.4 Joules

Thus, 1709.4 Joules is released when copper is cooled.

5 0
3 years ago
The atomic number of an element is determined by the number of electrons in the nucleus of the atom.
iren [92.7K]
A
The number of electrons/protons is the one that determines the atomic number of an element.
7 0
3 years ago
Read 2 more answers
If you place 1.0 L of ethanol (C2H5OH) in a small laboratory that is 3.0 m long, 2.0 m wide, and 2.0 m high, will all the alcoho
ankoles [38]

If you place 1.0 L of ethanol (C2H5OH) in a small laboratory that is 3.0 m long, 2.0 m wide, and 2.0 m high, will all the alcohol evaporate? If some liquid remains, how much will there be? The vapor pressure of ethyl alcohol at 25 °C is 59 mm Hg, and the density of the liquid at this temperature is 0.785g/cm^3 .

will all the alcohol evaporate? or none at all?

Answer:

Yes, all the ethanol present in the laboratory will evaporate since the mole of ethanol present in vapor is greater. The volume of ethanol left will therefore  be zero.

Explanation:

Given that:

The volume of alcohol which is placed in a small laboratory = 1.0 L

Vapor pressure of ethyl alcohol  at 25 ° C = 59 mmHg

Converting 59 mmHg to atm ; since 1 atm = 760 mmHg;

Then, we have:

= \frac{59}{760}atm

= 0.078 atm

Temperature = 25 ° C

= ( 25 + 273 K)

= 298 K.

Density of the ethanol = 0.785 g/cm³

The volume of laboratory = l × b × h

= 3.0 m × 2.0 m × 2.5 m

= 15 m³

Converting the volume of laboratory to liter;

since 1 m³ = 100 L; Then, we  have:

15 × 1000 = 15,000 L

Using ideal gas equation to determine the moles of ethanol in vapor phase; we have:

PV = nRT

Making n the subject of the formula; we have:

n = \frac{PV}{RT}

n = \frac{0.078 * 15000}{0.082*290}

n = 47. 88 mol of ethanol

Moles of ethanol in 1.0 L bottle can be calculated as follows:

Since  numbers of moles = \frac{mass}{molar mass}

and mass = density × vollume

Then; we can say ;

number of moles = \frac{density*volume }{molar mass of ethanol}

number of moles =\frac{0.785g/cm^3*1000cm^3}{46.07g/mol}

number of moles = \frac{&85}{46.07}

number of moles = 17.039 mol

Thus , all the ethanol present in the laboratory will evaporate since the mole of ethanol present in vapor is greater. The volume of ethanol left will therefore be zero.

5 0
2 years ago
1. The speed limit on most city streets is (25 miles). How many meters per minute
irina1246 [14]

Answer:

Speed = 670.56 \frac{m}{min}

Explanation:

Given

Speed = \frac{25 mi}{hr}

Required

Convert to meters per minutes

Speed = \frac{25 mi}{hr}

Start by converting the speed from miles to meters

1\ mile = 1609.34\ meters.

So, we have:

Speed = \frac{25 * 1609.34\ m}{hr}

Speed = \frac{40233.5\ m}{hr}

Next, we convert time from hours to minutes

1\ hour = 60\ minutes

So, we have:

Speed = \frac{40233.5\ m}{60\ min}

Speed = 670.56 \frac{m}{min}

<em>Hence, the equivalent of 25 miles per hour is 670.56 meters per minutes</em>

3 0
2 years ago
Please help :( this is for science.
elena55 [62]
Solar eclipse only i believe
4 0
2 years ago
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