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Nitella [24]
3 years ago
12

How many neutrons does element X have if its atomic number is 30 and its mass number is 70?

Chemistry
1 answer:
Yanka [14]3 years ago
3 0
The answer is 40.

We can solve this by finding out the number of protons, and neutrons. Atomic number of an element means the number of protons in that element. So, the atom has 30 protons if the atomic number is 30.

On the other hand, mass number is the total number of protons and neutrons, but not electrons, because they're too light comparing to the other 2. Therefore, we can simply solve the number of neutrons in the atom by subtracting the number of protons from the mass number. 70 - 30 = 40.

Therfore, the number of neutrons is 40.
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A 2.00-mol sample of hydrogen gas is heated at constant pressure from 294 K to 414 K. (a) Calculate the energy transferred to th
Furkat [3]

Answer:

a) The energy transferred is 6.91 kJ

b) The internal energy is 4.90 kJ

c) The work done on the gas is - 2.01 kJ

Explanation:

Step 1: Data given

Number of moles of hydrogen gas = 2.00 moles

Pressure = constant

Temperature is heated from 294 K to 414 K

Molar heat capacity of hydrogen gas = 28.8 J/mol*K

Step 2: Calculate the energy transferred to the gas by heat.

Q = n* Cp * ΔT

⇒with Q =the energy transferred

⇒with n = the number of moles = 2.00 moles

⇒with Cp = the Molar heat capacity of hydrogen gas = 28.8 J/mol*K

⇒ with ΔT = Temperature 2 - Temperature 1 = 414 - 294 = 120K

Q = 2.00 * 28.8 * 120

Q = 6912 J = 6.91 kJ

Step 3: Calculate the increase in its internal energy.

ΔEint = n*Cv*ΔT

⇒with ΔEint = the increase in its internal energy.

⇒with n = the number of moles = 2.00 moles

⇒with Cv = The constant volume = 20.4 J/mol*K

⇒with  ΔT = Temperature 2 - Temperature 1 = 414 - 294 = 120K

ΔEint = 2.00 * 20.4 * 120

ΔEint =4896 J = 4.90 kJ

Step 4: Calculate the work done on the gas.

Work done on the gas = -Q + ΔEint

W = -6.91 kJ + 4.90 kJ

W = -2.01 kJ

6 0
3 years ago
URGENT!!! A car engine uses the combustion of fuel to move a system of gears that move its wheels. Not all of the fuel's energy
Jobisdone [24]

Answer:sound energy and thermal energy

Explanation: cause coochie man

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Which element has 19 electrons surrounding the nuclei of its atoms?
QveST [7]
I think its potassium
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3 years ago
Describe how you would obtain a beaker of pure water from salty water
Maslowich

Answer:

You can boil or evaporate the water and the salt will be left behind as a solid. If you want to collect the water, you can use distillation. This works because salt has a much higher boiling point than water. One way to separate salt and water at home is to boil the salt water in a pot with a lid.

Explanation:

4 0
3 years ago
In today's experiment, Solutions A and B are prepared as follows.
hram777 [196]

Answer:

D. 0.160

Explanation:

The solution A is obtained adding 2.0mL of a solution of bromocresol green, 5.0mL of 1.60M HAc and 2.0mL of a solution of KCl. The solution is diluted to 50mL

That means the HAc is diluted from 5.0mL to 50.0mL, that is:

50.0mL / 5.0mL = 10 times.

And the final concentration of HAc must be:

1.60M / 10 times =

0.160M

Right answer is:

<h3>D. 0.160</h3>
3 0
3 years ago
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