Calcium-47, which decays by beta emission, has a half-life of 4.5 d. Part A Writ

Question

Calcium-47, which decays by beta emission, has a half-life of 4.5 d.

Part A

Write the nuclear equation for the beta decay of calcium-47.

Express your answer as a nuclear equation.

20Ca4721Sc47+1e0

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Part B

How many milligrams of an initial 31 mg of calcium-47 remain after 27 d ?

Express your answer to two significant figures and include the appropriate units.

m =

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Part C

How many days are required for 2.40 mg of calcium-47 to decay to 1.2 mg?

Express your answer to two significant figures and include the appropriate units.

t =

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Explanation / Answer

PART A:

Nuclear equation for beta decay of calcium-47 is

20Ca47 19K47 + 1e0

Here beta decay involves release of positron but not electron.

PART B:

given half life= 4.5 days

for 27 days, no. of half lifes= 27/4.5

=6

now,

for 6 half lifes,

31g/2= 15.5g

15.5/2= 7.75g

7.75g/2= 3.875g

3.875g/2= 1.9375g

1.9375g/2= 0.96875g

0.96875g/2= 0.484375g

hence 0.48g will remain finally.

PART C:

now,

2.40g/2= 1.2g

so, it takes one half life i.e., 4.5 days to decay.

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