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3 years ago

How do you find the number of neutrons in an element

Chemistry

2 answers:

viva [34]3 years ago

8 0

Answer: Atomic mass - Atomic number

Explanation:

To find the number of neutrons in an element, you want to subtract the atomic mass by the atomic number. The atomic number tells us the number of protons in the element. The atomic mass is the protons plus the neutrons. Therefore, you subtract the atomic mass and atomic number to cancel out the protons, leaving us with only neutrons.

e-lub [12.9K]3 years ago

6 0

Answer:

Mass number -Atomic number

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A reaction of 41.9 g of Na and 30.3 g of Br2 yields 36.4 g of NaBr . What is the percent yield?

Licemer1 [7]

Answer: The percent yield is, 93.4%

Explanation:

First we have to calculate the moles of Na.

$\text{Moles of Na}=\frac{\text{Mass of Na}}{\text{Molar mass of Na}}=\frac{41.9g}{23g/mole}=1.82moles$

Now we have to calculate the moles of $Br_2$

${\text{Moles of}Br_2} = \frac{\text{Mass of }Br_2 }{\text{Molar mass of} Br_2} =\frac{30.3g}{160g/mole}=0.189moles$

${\text{Moles of } NaBr} = \frac{\text{Mass of } NaBr }{\text{Molar mass of } NaBr} =\frac{36.4g}{103g/mole}=0.353moles$

The balanced chemical reaction is,

$2Na(s)+Br_2(g)\rightarrow 2NaBr$

As, 1 mole of bromine react with = 2 moles of Sodium

So, 0.189 moles of bromine react with = $\frac{2}{1}\times 0.189=0.378$ moles of Sodium

Thus bromine is the limiting reagent as it limits the formation of product and Na is the excess reagent.

As, 1 mole of bromine give = 2 moles of Sodium bromide

So, 0.189 moles of bromine give = $\frac{2}{1}\times 0.189=0.378$ moles of Sodium bromide

Now we have to calculate the percent yield of reaction

$\%\text{ yield}=\frac{\text{Actual yield}}{\text{Theoretical yield}}\times 100=\frac{0.353 mol}{0.378}\times 100=93.4\%$

Therefore, the percent yield is, 93.4%

3 0

3 years ago

PLEASE HELP ME WITH MY CHEM TEST

fgiga [73]

Answer:

8. 0.96

9. d

10b

11. 3

12 d

Explanation:

4 0

3 years ago

The density of an element is 19.3 g/cm^3. What is its density in kg/m^3?

Karolina [17]

First, you need to know 1 kg = 10^3 g. And 1 m^3 = 10^6 m^3. So the 1 g/cm3 = 10^3 kg/m3. So the answer is 1.93*10^4 kg/m3.

5 0

3 years ago

If the density of a liquid 102g/cm^3, how many milligrams will be in 63 mL of that liquid?

Ede4ka [16]

Answer:

Explanation:

The mass of a substance when given the density and volume can be found by using the formula

mass = Density × volume

From the question

63 mL = 63 cm³

We have

mass = 102 × 63 = 6426

But 1 g = 1000 mg

6426 g = 6426000 mg

We have the final answer as

Hope this helps you

6 0

3 years ago

How many electrons in an atom can share the quantum numbers n = 2, l = 1?<br> 1<br> 3<br> 6<br> 10

Igoryamba

Principal quantum number is n = 2, principal quantum number gives the energy shells electrons reside in,
angular momentum quantum number , these are the number of subshells and gives how many subshells are there in energy shells, values for l range from 0 to n-1
magnetic quantum number -m- gives the specific orbital in the subshells and their orientation.
spin quantum number gives the spin of the electrons.

in this case, n = 2
the types of subshells in n=2 are 0 and 1
0 - s subshell
1 - p subshell
the specific number of orbitals are given by -l to +l
when l = 1
then -1, 0 and +1
therefore there are 3 orbitals in p subshell and orbitals are in 3 orientations
each orbital can hold a maximum of 2 electrons,
since there are 3 orbitals each holding 6, there are 6 electrons to which these quantum numbers are the same
answer is 6

7 0

3 years ago

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