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3 years ago

8

How long will it take the Sun to go around the galaxy once? a. 200 million years c. 100 thousand years b. 10 years d. 5 billion

years

2 answers:

USPshnik [31]3 years ago

4 0

200 million years it will take this long and this proves how long the sun will possibly last

kirill [66]3 years ago

3 0

The answer is 200 million years

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Which observation most likely indicates that only a chemical change has taken place

salantis [7]

The correct answer as to which observation most likely indicates that only a chemical change has taken place would that the change cannot be reversed.

When it comes to changes in a system, it can either be:

physical change
chemical change

When a substance undergoes a physical change, the original version of the substance can be recovered. In other words, physical changes can be reversible.

When a substance undergoes a chemical change, the original version cannot be recovered because an entirely new product would have been formed. In other words, chemical changes are irreversible.

Thus, once a change becomes irreversible, such a change is said to be a chemical change.

More on chemical change can be found here: brainly.com/question/1161517

4 0

2 years ago

What volume of solution must be added to 4.0 mol of NaCl to make a 1.2 M solution?

Aleksandr [31]

Answer:

$\boxed {\boxed {\sf 3.3 \ liters}}}$

Explanation:

Molarity is a measure of concentration in moles per liter.

$molarity=\frac{moles \ of \ solute}{liters \ of \ solution}}$

The solution has a molarity of 1.2 M or 1.2 moles per liter. There are 4.0 moles of NaCl, the solute. We don't know the liters of solution, so we can use x.

molarity= 1.2 mol/L
moles of solute= 4.0 mol
liters of solution =x

Substitute the values into the formula.

$1.2 \ mol/L = \frac{4.0 \ mol}{x}$

Since we are solving for x, we must isolate the variable. Begin by cross multiply (multiply the 1st numerator and 2nd denominator, then the 1st denominator and 2nd numerator.

$\frac {1.2 \ mol/L}{1}=\frac{ 4.0 \ mol}{x}$

$4.0 \ mol *1=1.2 \ mol/L *x$

$4.0 \ mol = 1.2 \ mol/L *x$

x is being multiplied by 1.2 moles per liter. The inverse of multiplication is division, so divide both sides by 1.2 mol/L

$\frac{4.0 \ mol}{1.2 \ mol/L} = \frac{1.2 \ mol/L *x}{1.2 \ mol/L}$

$\frac{4.0 \ mol}{1.2 \ mol/L}=x$

The units of moles (mol) will cancel.

$\frac{4.0 }{1.2 } \ L =x$

$3.33333333 \ L=x$

The original measurements both have 2 significant figures, so our answer must have the same. For the number we found, this is the tenths place.

The 3 in the hundredth place tells us to leave the 3 in the tenths place.

$3.3 \ L\approx x$

Approximately <u>3.3 liters of solution</u> are needed to make a 1.2 M solution with 4.0 moles of sodium chloride.

7 0

3 years ago

How does government ensure a safe environment for inverters?

Anestetic [448]

hope it helps please brainliest

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3 years ago

A runner wants to run 11.7 km. She knows that her running pace is 6.7 mph. How many minutes must she run?

Alona [7]

She should run for about 65mins

4 0

3 years ago

Name two compounds with more exothermic lattice energies than scandium oxide and justify your choice.

N76 [4]

Answer:

1 . $Al_2O_3$

2. $TiO_2$

Explanation:

The more stable the ionic compound, the more is it lattice energy.

The more the charge on the cation and the anion, the greater is the lattice energy.
The less the size of the cation and the anion, the greater is the lattice energy.

Scandium oxide ( $Sc_2O_3$ ) is an oxide in which $Sc^{3+}$ behaves as cation and $O^{2-}$ behaves as anion.

The compounds which has higher lattice energy than scandium oxide are:

1 . $Al_2O_3$

This is because the charge are same on the cation and the anion as in the case of the Scandium oxide but the size of the cation $Al^{3+}$ is smaller than $Sc^{3+}$ . Thus, this corresponds to higher lattice energy.

2. $TiO_2$

This is because the charge on the cation $Ti^{4+}$ is greater than that of $Sc^{3+}$ and also the size of the cation $Ti^{4+}$ is smaller than $Sc^{3+}$ . Thus, this corresponds to higher lattice energy.

3 0

3 years ago