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3 years ago

If an isotope of an element has 40 neutrons and a mass number of 79, how many electrons must it have?

Chemistry

1 answer:

34kurt3 years ago

5 0

Answer: 39 electrons

Explanation: Subtract 79 by 40 to get the atomic number (amount of protons) which is 39. The number of electrons must be the same as the number of protons if it's not an ionic compound so the amount of electrons is the same amount of protons.

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When a paper towel absorbs water, is it a physical or chemical change?

Nonamiya [84]

Answer:

It is a physical change.

Explanation:

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3 years ago

How many valence electrons are in an atom. Of each element in group 15 in the periodic table.

oee [108]

Answer:

Five

Explanation:

All group 15 elements have five valence electrons, but they vary in their reactivity.

6 0

3 years ago

Based on the following molecular weight data of polypropylene, determine the degree of polymerization Molecular Weight Range (g/

Lady bird [3.3K]

Answer:

785

Explanation:

Molecular. X. W

Weight

8000-16000 0.05 0.03

16000-24000. 0.017. 0.08

24000-32000. 0.22. 0.18

32000-40000. 0.25. 0.35

40000-48000. 0.22. 0.27

48000-56000. 0.09. 0.09

Mean weight X*M. W*M

12000. 600. 240

20000. 3200. 2000

28000. 6720. 5600

36000. 10080. 10800

44000. 8800. 11880

52000. 3640 3640

Total=33040g\mol 36240

Note before repeat molecular weight m= 3*12.01+6*1.008=

42.08g/mol

Degree of polymerization= total W*M/w=33040/42.08 =785

8 0

3 years ago

I need this answer ASAP

asambeis [7]

Answer:

B: Physical Science

Explanation:

The answer is physical science because you need to know the laws of physics and chemistry to know how a car works. Physical sciences = the sciences concerned with the study of inanimate natural objects, including physics, chemistry, astronomy, and related subjects.

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4 years ago

Ok true or false

Misha Larkins [42]

Answer:

1.True

2.True

3.True

4. True

5. True

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3 years ago