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3 years ago

Which of the following is the composition of an isotope of calcium (atomic number 20)?

Chemistry

2 answers:

elena-s [515]3 years ago

6 0

20 protons

25 neutrons

20 electrons

ivolga24 [154]3 years ago

5 0

20 protons

20 electrons ( as much elctrons as protons because there has to be same positive and negative to have a neutral atom)

And the number of neutrons depends of the mass number but in that case, I think that it's a Calcium atom (Ca) and so there are 20 netrons.

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Where is the friction that allows the skater to complete the move that is occurring in this image? a girl ice skating © Wildcow

adelina 88 [10]

Answer:

C. The point of contact between the skates and the ice

Explanation:

That is the only point of friction with the ice that provides the ability to complete the move.

4 0

4 years ago

Explain how lines latitude and longitude help people find locations on earth.

Bad White [126]

Latitude and longitude are the x and y axis on a grid. When you're trying to find a location on earth, you need to graph it, so you can pinpoint the location. There is no grid if there is no longitude and/or latitude lines. Without one of the lines, it would be very hard to graph, which will be difficult in finding locations on earth. But hey, I'm not too sure. I recommend looking at other people's answers too and searching it up.

8 0

3 years ago

Volume of a gas at STP, if its volume is 80.0 mL at 1.08 atm and –12.5oC.

vodomira [7]

Answer:

90.5mL is the volume of the gas at STP

Explanation:

It is possible to find volume of a gas when conditions of temperature and pressure change using combined gas law:

$\frac{P_1V_1}{T_1} =\frac{P_2V_2}{T_2}$

Where P is pressure, V is volume and T is absolute temperature. 1 is initial conditions and 2 final conditions.

If initial conditions are 1.08atm, 80.0mL and absolute temperature is (-12.5°C + 273.15) = 260.65K.

And STP are 1atm of pressure and 273.15K of absolute temperature. Replacing:

$\frac{1.08atm80.0mL}{260.65K} =\frac{1atmV_2}{273.15K}$

V₂ = <em>90.5mL is the volume of the gas at STP</em>

7 0

3 years ago

Read 2 more answers

How many unit cells share an atom that is located at the center of a cube edge of a unit cell?

andre [41]

Answer:

zero

Explanation:

In a unit cell, an atom that is located at the center of a cube edge is not involved in sharing unit cells because a central atom of a unit cell belongs to the entire cell and only to that unit cell of the lattice.

Hence, the center atom of a unit cell do not share any unit cell and the correct answer is "Zero".

6 0

3 years ago

Charcoal from the dwelling level of the Lascaux Cave in France gives an average count of 0.97 disintegrations of ^14 C per minut

Verdich [7]

Answer:

Explanation:

count given by old sample = .97 disintegrations per minute per gram

count given by fresh sample = 6.68 disintegrations per minute per gram

Half life of radioactive carbon = 5568 years

rate of disintegration

dN / dt = λ N