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3 years ago

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Chemistry

1 answer:

Alecsey [184]3 years ago

8 0

Don't we all.................

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How many neutrons does element X have if its atomic number is 30 and its mass number is 70?

Yanka [14]

The answer is 40.

We can solve this by finding out the number of protons, and neutrons. Atomic number of an element means the number of protons in that element. So, the atom has 30 protons if the atomic number is 30.

On the other hand, mass number is the total number of protons and neutrons, but not electrons, because they're too light comparing to the other 2. Therefore, we can simply solve the number of neutrons in the atom by subtracting the number of protons from the mass number. 70 - 30 = 40.

Therfore, the number of neutrons is 40.

3 0

3 years ago

What is the (OH-) in a solution with a pOH of 6.48

inn [45]

Through manipulation of equations, we are able to obtain the equation:

$-pOH= log [ OH^{-}]$

Then we can transform the equation into:

$[ OH^{-}]= 10^{-pOH}$

Then we are able to plug in the pOH and directly get [OH-]:

$[ OH^{-}] = 10^{-6.48}$

$[ OH^{-}]=3.31* 10^{-7} M$

3 0

3 years ago

A 0.75M solution of CH3OH is prepared in 0.500 kg of water. How many moles of CH3OH are needed?

4vir4ik [10]

Answer:

We need 0.375 mol of CH3OH to prepare the solution

Explanation:

For the problem they give us the following data:

Solution concentration 0,75 M

Mass of Solvent is 0,5Kg

knowing that the density of water is 1g / mL, we find the volume of water:

$d = \frac{g}{mL} \\\\ V= \frac{g}{d} = \frac{500g}{1 \frac{g}{mL} } = 500mL = 0,5 L$

Now, find moles of $CH_{3} OH$ are needed using the molarity equation:

$M = \frac{ moles }{ V (L)} \\\\\\molesCH_{3}OH = M . V(L) = 0,75 M . 0,5 L\\\\molesCH_{3}OH = 0,375 mol$

therefore the solution is prepared using 0.5 L of H2O and 0.375 moles of CH3OH, resulting in a concentration of 0,75M

5 0

3 years ago

Increasing the ? of a solvent increases the solubility of the solute

Gelneren [198K]

There are a lot of ways to increase the solubility of the solute. <span>Increasing the temperature, mixing time and surface area of a solvent increases the solubility of the solute</span>

7 0

3 years ago

Read 2 more answers

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tino4ka555 [31]

The answer is number 2

4 0

3 years ago