The answer to this question would be: 3.125%

Half-life is the time needed for a radioactive molecule to decay half of its mass. In this case, the strontium-89 is already gone past 5 half lives. Then, the percentage of the mass left after 5 half-lives should be:
100%*(1/2^5)= 100%/32=3..125%

5 0

3 years ago

An air sample contains 0.044% CO2? If the total pressure is 750 mm Hg. What is the partial pressure of CO2?2?

Aleksandr [31]

Partial pressure=mole fraction×Pt
x=0.044÷44(maolarmass of CO2)×Pt
x=0.044÷(44)2×Pt
x=5×10^-4×Pt
x=5×10^-4×Pt
where Pt:1atm=760mmHg
xatm=750mmHg
750×1÷760=0.99
now;5×10^-4×099=4.95×10^-4.
Pt=4.95×10^-4

8 0

3 years ago

How much calcium can be recovered from 75.0g of calcium fluoride

7nadin3 [17]

38.46g

Explanation:

Given parameters:

Mass of CaF₂ = 75.0g

Unknown:

Mass of calcium that can be recovered = ?

Solution:

This is a mass percentage problem and we need to solve it accordingly.

To solve this problem;

Find the molar mass of CaF₂

Find the ratio between the molar mass of Ca and that of CaF₂

Multiply by the given mass

Molar mass of CaF₂ = 40 + (2 x 19) = 78g/mol

Mass of calcium = $\frac{40}{78}$ x 75 = 38.46g

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Mass percentage brainly.com/question/8170905

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3 0

3 years ago