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3 years ago

The discovery that uranium is a radioactive element was made by Marie Curie. True or False

Chemistry

2 answers:

Ivanshal [37]3 years ago

8 0

Answer:

True

Explanation:

navik [9.2K]3 years ago

4 0

Your answer is true.

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Using the following equation for the combustion of octane, calculate the heat associated with the combustion of 100.0 g of octan

Sonja [21]

Answer: B) -4819 kJ

Explanation:

The balanced reaction for combustion of octane is:

$2C_8H_{18}+25O_2\rightarrow 16CO_2+18H_2O$ $\Delta H^0_{rxn}=-11018kJ$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

given mass of octane = 100.0 g

Molar mass of octane = 114.33 g/mol

Putting in the values we get:

$\text{Number of moles}=\frac{100.0g}{114.33g/mol}=0.8747moles$

According to stoichiometry:

2 moles of octane give heat = -11018 kJ

Thus 0.8747 moles of octane give = $\frac{-11018}{2}\times 0.8747=-4819kJ$

Thus -4819 kJ of heat is released by 100.0 g of octane assuming complete combustion.

5 0

4 years ago

Read 2 more answers

If the half life of a radioactive isotope is 1 day, then how much of the original isotope remains at the end of two days?

ikadub [295]

$\huge{\color{magenta}{\fcolorbox{magenta}{black}{\huge{\color{white}{\fcolorbox{aqua}{black}{✿ᴀɴsᴡᴇʀ✿}}}}}}$

25%

Explanation:

In a half life of a radioactive isotope is 1 day,it means it loses its half mass each day

We a formula for N half life

$\sf { \frac{1}{2} }^{n}$

where n is the number of days

Here the isotope is kept for 2 days

so it's left over mass will be

$\sf { (\frac{1}{2}) }^{2} \\ \\ \\ \frac{1}{2} \times \frac{1}{2} \\ \\ \sf \frac{1}{4}$

It's left over mass 1/4th of the original mass

Now, we need to find it's percentage by multiplying with 100

$\sf \frac{1}{4} \times 100 \%\\ \\ \sf \cancel\frac{100}{4} \% \\ \\ \sf 25\%$

So 25% mass will be left after 2 day of half life radioactive isotope.

8 0

2 years ago

Read 2 more answers

How has the pressure of the gas changed?

9966 [12]

Cold you please repost the question
THIS IS A QUESTION REGARDING
ideal gas equation
which states that
PV = nRT
where;
P : Pressure (atm)
V : Volume (litres)
n : Number of moles of that gas(mol)
R : Real gas constant = 0.0821
T : Temperature of that gas(Kelvin)
hope this helps

6 0

3 years ago

Which substance has non polar covalent bonds

Sati [7]

Cl2 is the right answer since the molecule is composed of two chlorines.

4 0

3 years ago

How many additional electrons does this atom of oxygen need in its valence shell to satisfy the octet rule?

vfiekz [6]

Answer:

Explanation:

cause it is what it is :> mark me brainlest

5 0

4 years ago