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spayn [35]
2 years ago
7

What is the atomic number for an element whose mass number is 78,

Chemistry
2 answers:
Ann [662]2 years ago
5 0

Answer:

protons = atomic numbermass number = protons + neutronsatomic number = mass number - neutrons = 78-38 = 40

Explanation:

murzikaleks [220]2 years ago
4 0

Answer:

48

Explanation:

i took the test lolll

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Lead(II) oxide from an ore can be reduced to elemental lead by heating in a furnace with carbon. Calculate the expected yield of
Lelu [443]

Answer:

53kg is the expected yield of lead

Explanation:

Firstly, in order to solve this question, we need to write the equation of reaction correctly. This is as follows:

PbO(s) + C(s) ---> Pb(l) + CO(g)

We proceed from here. We should get the limiting reactant but this can only be obtained by getting the number of moles of each reactant present.

The formula to use across all boards is that the number of moles is the mass of each of the reactant divided by the molar mass of each of the reactant.

For PBO, mass is 57kg = 57000g

Molar mass of PBO = 223.20g/mol

The number of moles is thus 57,000/223.2 = 255.37 moles

For carbon, mass is also 57kg = 57000g

Molar mass is 12g/mol

Number of moles of carbon = 57000/12 = 4750 moles

From the number of moles, we can see that the number of moles of Carbon is greater than that of PbO. This means that PbO is the limiting reagent.

Hence we use it to calculate percentage yield.

The number of moles of lead formed is the same of number of moles of lead oxide = 255.37 since we have mole ratio of 1 to 1

The molar mass of lead is 207.20g/mol

The mass of lead formed is = moles of lead formed * molar mass of lead = 207.20 * 255.37 = 52,912g which is approximately 53kg

Hence the expected yield is 53kg

6 0
3 years ago
Scientists have categorized trees based on whether they keep or lose their leaves each year. Another logical way to categorize t
Zolol [24]

Answer:

D

Explanation:

I think but it is an better attempt than the other guy answer.

5 0
2 years ago
What is the electron configuration of an element with atomic number 20?
VARVARA [1.3K]
1s2,2s2.2p6,3s2,3p6,3d4,4s2
8 0
3 years ago
Read 2 more answers
2
dexar [7]

Answer:

i do not know

Explanation:

6 0
2 years ago
How many standard amino acids are there in the human body?
Whitepunk [10]

Answer:

-Theres 20 amino acids in the human body

-The least number of amino acids in a polypeptide are 10

Explanation:

5 0
3 years ago
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