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3 years ago

Help please!!

Chemistry

1 answer:

frez [133]3 years ago

7 0

Answer:

6.25%

Explanation:

Given data:

Half life of lutetium-117 = 6.75 days

Percentage remaining after 27 days = ?

Solution;

Number of half lives = Time elapsed / half life

Number of half lives = 27 days / 6.75 days

Number of half lives = 4

At time zero = 100%

At first half life = 100%/2 = 50%

At second half life = 50%/2 = 25%

At 3rd half life = 25%/2 = 12.5%

At 4th half life = 12.5%/2 = 6.25%

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Zn(OH)2+H3PO4>Zn3(PO4)2+H2O

pshichka [43]

3Zn(OH)₂ + 2H₃PO₄ → Zn₃(PO₄)₂ + 6H₂O

Explanation:

To balance this equation, we must understand that in every chemical reaction, the number of atoms is usually conserved.

The total number of atoms on the reactant and product sides must be equal and the same.

Zn(OH)₂ + H₃PO₄ → Zn₃(PO₄)₂ + H₂O

We are are going to use simple, solvable algebraic equations to balance this;

aZn(OH)₂ + bH₃PO₄ → cZn₃(PO₄)₂ + dH₂O

a, b,c and d are the number of coefficient that will balance this equation:

Conserving Zn ; a = 3c

O: 2a + 4b = 8c + d

H: 2a + 3b = 2d

P: b = 2c

let c = 1;

a = 3

b = 2

solving for d;

2d = 2(3) + 3(2)

d = 6

3Zn(OH)₂ + 2H₃PO₄ → Zn₃(PO₄)₂ + 6H₂O

learn more:

Balanced equation brainly.com/question/2612756

#learnwithBrainly

6 0

3 years ago

How many molecules does 1 mole of Oz gas have?

Katen [24]

awnser : 6.02×1023 molcules

4 0

3 years ago

Read 2 more answers

How many electrons can be contained in the second energy level?

Lelechka [254]

Its D for the second energy level, but the first energy level is 2.

3 0

3 years ago

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What is the number of protons and electrons in a neutral atom of<br> Lithium?

nadya68 [22]

If you look at the periodic table you will see the atomic number (the smaller number) which is 3. that identifies how many protons there are. since the lithium is neutral that means there’s a same amount of electrons.

therefore there’s 3 electrons and 3 protons

3 0

3 years ago

Write the balanced equation for the combustion of isooctane to produce water vapor and carbon dioxide gas.Assuming gasoline is i

tangare [24]

Answer:

The yield is 16 moles of CO2 per 2 moles of isooctane.

The mass of CO2 is 1.15 billion tonnes

Explanation:

First we set the unbalanced equation:

$C_{8}H_{18} + O_{2} \longrightarrow CO_{2} + H_{2}O$

Now we proceed to balance the equation:

$2C_{8}H_{18} + 25O_{2} \longrightarrow 16CO_{2} + 18H_{2}O$

With the equation balanced, we see that the theoretical yield is 16 moles of CO2 per 2 moles of isooctane and we can proceed to make calculations with the following data:

$\rho _{C_{8}H_{18}}=0.69 g/mL\\Consumption: 142.86x10^{9} gal\\1gal=3785.41 mL\\M_{C_{8}H_{18}}=114.23g/mole\\M_{CO_{2}}=44.01g/mole\\$

Knowing the different relations between mass, density and molar mass, we have the following results:

$V_{C_{8}H_{18}}=5.41x10^{14}mL\\m_{C_{8}H_{18}}=3.73x10^{14}g\\n_{C_{8}H_{18}}=3.27x10^{12}mole\\n_{CO_{2}}=2.62x10^{13}mole\\m_{CO_{2}}=1.15x1015g\\m_{CO_{2}}=1.15x10^{9}tonnes$

8 0

4 years ago