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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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If the balanced chemical reaction for the formation of Li2O is 4 Li(s) + O2(g) → 2 Li2O(s), how many molecules of Li2O(s) would
Marta_Voda [28]

The molecules of Li₂O that would produce if you used up 6 atoms of Li(s) is 3.

<h3>What is Lithiumdioxide?</h3>

It is an unstable inorganic and radical compound, used in the manufacture of glass and ceramic.

The balanced equation

\rm 6 Li(s) + O_2(g) \rightarrow 3 Li_2O(s)

If the atoms of lithium moves up to 6 the lithium oxide molecules will be 3, as you can see in the equation.

Thus, the molecules of Li will be 3.

Learn more about lithium dioxide

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5 0
3 years ago
Assume that 50.0mL 50.0mL of 1.0MNaCl(aq) 1.0MNaCl(aq) and 50.0mL 50.0mL of 1.0M AgNO 3 (aq) 1.0MAgNO3(aq) were combined. Accord
S_A_V [24]

Answer:

The amount of precipitate formed would 7.175 grams of silver chloride.

Explanation:

Moles (n)=Molarity(M)\times Volume (L)

Moles of NaCl = n

Volume of NaCl solution = 50.0 mL = 0.050 L

Molarity of the hydrogen peroxide = 2.0 M

n=2.0 M\times 0.050 L=0.100 mol

Moles of silver nitarte = n'

Volume of silver  nitrate solution = 50.0 mL = 0.050 L

Molarity of the silver nitrate = 1.0 M

n'=1.0 M\times 0.050 L=0.050 mol

NaCl(aq)+AgNO_3(aq)\rightarrow AgCl(s)+NaNO_3(aq)

According to reaction, 1 mole of of silver nitrate reacts with 1 mole of NaCl. Then 0.050 mole of silve nitrate will :

\frac{1}{1}\times 0.050 mol=0.050 mol of NaCl

This means that silver nitrate is in limiting amount and NaCl is in excessive amount.

So, the amount of AgCl depends upon amount of silver nitrate.

According to reaction, 1 mole of silver nitrate gives 1 mole of AgCl.

Then 0.050 moles of silver nitrate will give;

\frac{1}{1}\times 0.050 mol=0.050 mol of AgCl

Mass of 0.050 moles of AgCl ;

0.050 mol\times 143.5 g/mol=7.175 g

The amount of precipitate formed would 7.175 grams of silver chloride.

8 0
3 years ago
If 0.380 mol of barium nitrate is allowed to react with an excess of phosphoric acid, how many moles of barium phosphate could b
Vladimir [108]

If 0.380 mol of barium nitrate is allowed to react with an excess of phosphoric acid, 0.127 moles of barium phosphate could be formed.

<h3>How to calculate number of moles?</h3>

The number of moles of a compound can be calculated stoichiometrically as follows:

Based on this question, the following chemical equation is given:

Ba (NO3)2+ H3PO4 → Ba3(PO4)2+ HNO3

The balanced equation is as follows:

3Ba(NO3)2 + 2H3PO4 → Ba3(PO4)2 + 6HNO3

3 moles of barium nitrate produces 1 mole of barium phosphate

Therefore, 0.380 moles of barium nitrate will produce 0.380/3 = 0.127moles of barium phosphate.

Learn more about stoichiometry at: brainly.com/question/9743981

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