21: potassium has 20 neutrons
22: is d
Answer:

Explanation:
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In this case, we use the Avogadro's number to compute the molecules of C2F4 whose molar mass is 100 g/mol contained in a 485-kg sample as shown below:

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Muscle tissue
Explanation: Muscle tissue is a soft tissue that makes up most of the tissues in the muscles of the human muscular system. It is the only type of tissue that has cells with the ability to contract. Skeletal muscle tissue is attached to bones by tendons.
Answer:
2.52 atm
Explanation:
Change C to K.
Solve for P1=P2V2T2/V1T1
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Answer: C
Explanation:
The impact she has on the environment