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2 years ago

Why is it so difficult

Chemistry

2 answers:

Leokris [45]2 years ago

7 0

Chemistry is very fun but yet so difficult

Sergeeva-Olga [200]2 years ago

5 0

Because teachers don’t really understand it all that well themselves so they can’t teach it effectively

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a radioisotope has a half life of three hours how much of a 120g sample remains after 9 hours. what will the g amount be after 3

aksik [14]

$\huge\boxed{♔︎Answer♔︎}$

60g after 3 hours, 30g after 6 hours and 15g after 9 hours

Explanation:

Weight of the radioactive sample = 120g

half life time period = 3 hours

(a) The weight of sample after 3 hours

$\textsf{ No. of half lives} = \sf \cancel\frac{3}{3} = 1$

The fraction of sample left

$\sf { \frac{1}{2} }^{1} = \frac{1}{2}$

Mass of the sample left

$\sf \frac{1}{2} \times 120 = \cancel\frac{120}{2} = 60g$

60g of sample is left after 3 hours

(b) The weight of sample after 6 hours

$\textsf{ No. of half lives} = \sf \cancel\frac{6}{3} = 2$

The fraction of the sample left

$\sf { \frac{1}{2} }^{2} = \frac{1}{2} \times \frac{1}{2} = \frac{1}{4}$

Mass of the sample left

$\sf \frac{1}{4} \times 120 = \cancel\frac{120}{4} = 30g$

30g of sample is left after 6 hours

$\textsf {No. of half lives} = \sf \cancel\frac{9}{3} = 3$

The fraction of sample left

$\sf { \frac{1}{2} }^{3} = \frac{1}{2} \times \frac{1}{2} \times \frac{1}{2} = \frac{1}{8}$

Mass of sample left

$\sf \frac{1}{8} \times 120 = \cancel \frac{120}{8} = 15g$

15g of sample is left after 9 hours.

3 0

2 years ago

Nén 10l khi ở áp suất 1atn,nhiệt đọ 27độ c để thể tích của nó giảm còn 5 lít quá trình nén nhanh nên nhiệt độ tăng đến 57 độ c á

mariarad [96]

Answer:

Explanatio

pV=nRT

=>n = 0.4(mol)

=>p 2= 2.34 atm

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3 years ago

Lighting a match is an example of what kind of energy conversion?

Alika [10]

Answer:

Mechanical Energy to Thermal Energy

When you strike a match, it moves through the air until it rubs against a surface. The rubbing produces the heat required to light the match. This is a transformation from mechanical energy to thermal (heat) energy.

Explanation:

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3 years ago

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Given the balanced equation representing a reaction:

romanna [79]

The answer should be neutralization

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3 years ago

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Copper atoms are oxidised at the positive electrode to Cu2+ ions, as shown in the half equation.

mafiozo [28]

(anode +) Cu⁰(s) - 2e⁻ → Cu²⁺(aq)

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4 years ago