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3 years ago

Why are relative atomic masses on the periodic tables not whole numbers?

Chemistry

2 answers:

Kobotan [32]3 years ago

6 0

Answer:

They are averages.

Explanation:

atomic numbers on periodic tables are derived from the average value of all the isotopes of the element. So being averages they are sometimes not integers.

Darya [45]3 years ago

4 0

Answer:

The sum of the number of protons and neutrons in an atom is called the mass number. Atomic mass is never an integer number for several reasons: The atomic mass reported on a periodic table is the weighted average of all the naturally occurring isotopes. Being an average it would be most unlikely to be a whole number.

Explanation:

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How many molecules of co2 are in a 500. 0 ml container at 780 mm hg and 135°c? 8. 76 × 1021 molecules 9. 23 × 1021 molecules 5.

Aloiza [94]

ok we have to use the formula PV=nRT

p=Pressure (must be converted to atm)= 780 mmHg

1 amt= 760 mmHg use this as a conversion factor

780 mmHg (1 atm/760 mmHg)= 1.026

V= Volume= 5.00 mL = o.5 L

n=number of moles which we have to find first

R= 0.0821

T(convert to Kelvins by adding 273.15 to the celsius temperature)= 135 C + 273.15= 408.15 k

Now plug in->

(1.026 atm)(o.5 L)= n(0.0821)(408.15 K)

(1.026 atm)(0.5 L)= n(33.509115)

(0.513)= n(33.509115)

n(number of moles)= 0.01532 mol

Now we have to convert to moles using Avagodro's number which states that 1 mol = 6.022 x 10^23 molecules or atoms

So 0.01532 mol (6.022 x 10^23 number of molesules)/ (1 mol) = 9.225704 x 10^21 = 9.226 x 10^21 colecules

Step 2

You must transfer pressure into pascals, 780 mm Hg = 103991 Pa

135*C = 408.15 k

then from the equation pV = nRt

n = pV / RT (T in Kelvins, V in M^3)

n = 103991 x 500 x 10^-6 / (8.314 x 408.15)= 0.015322 moles of N2

1 mol of everything is 6.022 x 10^23 particles, so 0.15322 moles is 0.15322 x 6.022 x 10^23 = 9.2269084 x 10^21 molecules

Explanation:

Hope this helps :)

5 0

2 years ago

Which of the following has to remain constant to allow you to use the combined gas law for calculations?

Mazyrski [523]

Answer:

Amount of gas

Explanation:

The combined gas law has to do with pressure, volume, and temperature. All of them can be a variable that you have to solve for. However, amount of gas is not a variable you can solve for, which means it must remain constant.

4 0

3 years ago

The combustion of 1 mol ch4 releases 803 kj of energy. how much energy is produced from the combustion of 5.00 mol ch4.

Annette [7]

Answer : The energy produced from the combustion of 5 mole $CH_4$ is $4015KJ$

Solution : Given,

Released energy = 803 KJ

The balanced combustion reaction is,

$CH_4+2O_2\rightarrow CO_2+2H_2O$

As per the question,

1 mole of $CH_4$ releases energy = 803 KJ

5 mole of $CH_4$ produced energy = $\frac{5mole}{1mole}\times 803KJ=4015KJ$

Therefore, the energy produced from the combustion of 5 mole $CH_4$ is $4015KJ$

7 0

4 years ago

Find the volume of 3.011x1023 molecules of O2 at STP.

lord [1]

Answer:

6.022 x 1023 molecules = 1 Mole O2 = 22.4L

3.022 x 1023 molecules = 1/2 Mole O2 = 11.2L

The answer is 11.2 Litres

Explanation:

8 0

2 years ago

What type of compound is fe3n2

Shkiper50 [21]

Fe3N2, also known as Iron (II) nitride, is an ionic compound.

Ionic compounds are compounds that consists of metals and non-metals bonded with ionic bonds. The metal ion gives up electron(s) to the non-metals.

Since iron is a metal and nitrogen is an non-metal, the bond they would form would be an ionic bond. Iron gives up 2 electrons to form iron(II) ion, while nitrogen gains 3 electrons to form nitride ion. Since one iron cannot let a nitrogen gain 3 electrons, so in the compound, there would be 3 iron (ii) ions that has given up 6 electrons in total while 2 nitride ions have gained 6 electrons in total.

8 0

3 years ago