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mafiozo [28]
3 years ago
15

If a 520 mg sample of technetium-99 is used for diagnostic procedure, how much of Tc-99 remains after 30.0h? Half life of Tc-99

is 6.0 hours.
Chemistry
1 answer:
k0ka [10]3 years ago
4 0
16.25 mg
I have attached an image of the half life formula.
In this problem, N0 would be 520, since that is the initial amount.
t = 30.0 Hours
t 1/2 = 6.0 hours
Now plug everything into the equation. You get 16.25 mg. No

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11. The back part of the cerebrum deals with hearing<br><br> True<br><br> False
Sunny_sXe [5.5K]

Answer:

The answer is: True

5 0
3 years ago
1. Discuss briefly system and surrounding using suitable examples, highlighting heat transfers. 14 marks​
lisabon 2012 [21]

A system is a part of the <em>physical</em> universe defined <em>arbitrarily</em> for observation purposes.

Boundaries are a part of the <em>physical</em> universe that are around the system.

In a scientific sense, a system is a part of the <em>physical</em> universe whose boundaries, that is, the limit between the system and its surroundings, are defined <em>arbitrarily</em> for observation purposes.

A system contains at least a model, represented in a phenomenological way, and it can be isolated (no mass nor energy interactions), closed (no mass interactions) or open.

The surroundings are a part of the <em>physical</em> universe that are around the system.

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3 0
3 years ago
During an investigation, a student burns magnesium to form magnesium oxide. The starting mass of magnesium is measured as 21.3 g
enot [183]

Answer:

Percentage yield = 85.2%

Explanation:

Given data:

Mass of Mg = 21.3 g

Actual yield of MgO = 30.2 g

Percentage yield = ?

Solution:

Chemical equation:

2Mg + O₂ → 2MgO

Number of moles of Mg = mass/molar mass

Number of moles of Mg = 21.3 g / 24.3 g/mol

Number of moles of Mg = 0.88 mol

Now we will compare the moles of MgO with Mg.

                 Mg           :               MgO

                 2               :               2

                0.88             :             0.88

Mass of MgO:           

Mass of MgO= moles × molar mass

Mass of MgO= 0.88 mol × 40.3g/mol

Mass of MgO =  35.46 g

Actual yield of MgO = 30.2 g

Percentage yield:

Percentage yield = Actual yield/theoretical yield × 100

Percentage yield = 30.2 g/ 35.46 g × 100

Percentage yield = 85.2%

3 0
4 years ago
How many moles of calcium carbonate-CaCO3 = 4.15 g​
marin [14]

Answer:

Number of moles = 0.042 mol

Explanation:

Given data:

Number of moles = ?

Mass of calcium carbonate = ?

Solution:

Formula:

Number of moles = mass/ molar mass

now we will calculate the molar mass of calcium carbonate.

atomic mass of Ca = 40 amu

atomic mass of C = 12 amu

atomic mass of O = 16 amu

CaCO₃ = 40 + 12+ 3×16

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CaCO₃ = 100 g/mol

Now we will calculate the number of moles.

Number of moles = 4.15 g / 100 g/mol

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3 0
4 years ago
Which radioactive emission has the smallest (least) mass? Question options:
Tems11 [23]

Answer:

The answer is D. gamma rays

Explanation:

A radioactive atom can have three different types of emission:

alpha particles (α) = they have a mass of 4 amu and they have a very low penetrating power.

Beta particles (β) = they have 5x10^{-4} amu and they have an intermediate penetrating power

Gamma rays (γ) = they are not particles basically just energy so its mass is ≈ 0 and its penetrating power is higher

For this reason Gamma emissions (γ) has the smallest mass value.

8 0
3 years ago
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