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Jlenok [28]
3 years ago
15

How many elements are man made

Chemistry
2 answers:
Zinaida [17]3 years ago
8 0
On the periodic tables, there are 26 manmade elements that have atomic numbers from 93 to 118.
siniylev [52]3 years ago
6 0
26 elements are man-made ..........
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Photosynthesis is the process by which plants, some bacteria and some protistans use the energy from sunlight to produce glucose from carbon dioxide and water.

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Which of the following is a measurement of an object's mass?
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10 Kilograms

Explanation:

"millimetres" is a unit of measurement and is used for measuring distances.

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2 years ago
Calculate the number of hydrogen atoms present in 40g of urea, (NH2)2CO
tekilochka [14]

Answer: There are 16.14 \times 10^{23} atoms of hydrogen are present in 40g of urea, (NH_{2})_{2}CO.

Explanation:

Given: Mass of urea = 40 g

Number of moles is the mass of substance divided by its molar mass.

First, moles of urea (molar mass = 60 g/mol) are calculated as follows.

Moles = \frac{mass}{molar mass}\\= \frac{40 g}{60 g/mol}\\= 0.67 mol

According to the mole concept, 1 mole of every substance contains 6.022 \times 10^{23} atoms.

So, the number of atoms present in 0.67 moles are as follows.

0.67 mol \times 6.022 \times 10^{23} atoms/mol\\= 4.035 \times 10^{23} atoms

In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.

4 \times 4.035 \times 10^{23} atoms\\= 16.14 \times 10^{23} atoms

Thus, we can conclude that there are 16.14 \times 10^{23} atoms of hydrogen are present in 40g of urea, (NH_{2})_{2}CO.

7 0
2 years ago
[BrO- ]initial is 0.56 M. 33 seconds later [BrO- ] is 0.14 M. What is the rate of change of [BrO- ] in M/s? (The brackets, [ ],
iVinArrow [24]

Answer:

0.013 M/s

Explanation:

Given data

  • Initial concentration of BrO⁻: 0.56 M
  • Final concentration of BrO⁻: 0.14 M
  • Time (t): 33 s

Since the final concentration of BrO⁻ is lower than the initial concentration of BrO⁻, BrO⁻ is dissapearing. The rate of dissapearance of BrO⁻ is:

rBrO⁻ = - Δ [BrO⁻] / t

rBrO⁻ = - (0.14 M - 0.56 M)/ 33 s

rBrO⁻ = 0.013 M/s

3 0
2 years ago
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