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Ghella [55]
3 years ago
15

(25 points) A certain isotope of technetium has a half-life of 8 hours. How much of a 40 gram sample will be left after 16 hours

?
A. 10 grams
B. 40 grams
C. 5 grams
D. 20 grams
Chemistry
1 answer:
gtnhenbr [62]3 years ago
6 0

Answer:

A) 10 grams

Explanation:

16 hours = 2 half lives

This means that the number is divided in half twice.

40/2 = 20

20/2 = 10

I hope this helps!! :)

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Answer:

8239.2g

Explanation:

Given parameters:

Number of atoms in Br  = 6.2 x 10²⁵atoms

Unknown:

Mass of Br = ?

Solution:

From mole concepts, we know that:

       1 mole of a substance contains 6.02 x 10²³ atoms/mol

 Molar mass of Br  = 80g/mol

6.2 x 10²⁵atoms  x \frac{1}{6.02 x 10^{23} } \frac{mol}{atoms} x  80 x \frac{g}{moles}  

          = 8239.2g

8 0
3 years ago
3Fe+4H2O(yields) Fe3O4+4H2. What is the mole ratio of Fe3O4 to Fe?
WINSTONCH [101]

<u>Answer:</u> The correct answer is Option A.

<u>Explanation:</u>

Mole ratio is defined as the ratio between the stoichiometric coefficients of the molecules present in the chemical reaction.

For the given balanced chemical equation:

3Fe+4H_2O\rightarrow Fe_3O_4+4H_2

By Stoichiometry of the reaction:

3 moles of iron metal reacts with 4 moles of water to produce 1 mole of iron oxide and 4 moles of hydrogen gas.

The mole ratio of Fe_3O_4:Fe=1:3

Hence, the correct answer is Option A.

7 0
3 years ago
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Abigail obtained 36.6 grams of calcium carbonate after performing a reaction. From her calculations, she knew she should have ob
Zielflug [23.3K]

Answer:

it would be 1

Explanation:

3 0
3 years ago
Sodium carbonate reacts with silver nitrate according to the following balanced equation: Na2CO3 (s) + 2 AgNO3 (aq) → Ag2CO3 (s)
klemol [59]

Answer:

a) 2.01 g

Explanation:

  • Na₂CO₃ (s) + 2AgNO₃ (aq) → Ag₂CO₃ (s) + 2NaNO₃

First we <u>convert 0.0302 mol AgNO₃ to Na₂CO₃ moles</u>, in order to <em>calculate how many Na₂CO₃ moles reacted</em>:

  • 0.0302 mol AgNO₃ * \frac{1molNa_2CO_3}{2molAgNO_3}  = 0.0151 mol Na₂CO₃

So the remaining Na₂CO₃ moles are:

  • 0.0340 - 0.0151 = 0.0189 moles Na₂CO₃

Finally we <u>convert Na₂CO₃ moles into grams</u>, using its <em>molar mass</em>:

  • 0.0189 moles Na₂CO₃ * 106 g/mol = 2.003 g Na₂CO₃

The closest answer is option a).

8 0
3 years ago
How many moles of water are produced when 3.45 moles of KMnO4 react? Give your answer to the nearest 0.1 moles. moles H2O
andrew11 [14]

Answer:

13.8 moles of water produced.

Explanation:

Given data:

Moles of KMnO₄ = 3.45 mol

Moles of water = ?

Solution:

Chemical equation:

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Moler ratio of water and KMnO₄:

             KMnO₄       :        H₂O

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Hence, 3.45 moles of KMnO₄ will produced 13.8 mol of water.

7 0
3 years ago
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