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kumpel [21]
3 years ago
5

Conclusions related to historical events are limited to subjective evaluation of the existing evidence because _____. they canno

t be repeated they don't need to be tested hypotheses cannot be developed that is good enough
Chemistry
2 answers:
Vera_Pavlovna [14]3 years ago
5 0
<span>This is not actually a chemistry question but okay:

Conclusions related to historical events are limited to subjective evaluation of the existing evidence because </span>they cannot be repeated. 
masya89 [10]3 years ago
4 0

Answer:

they cannot be repeated

Explanation:

A historical event can not be repeated so that it is possible to study it. For this reason, when studying a historical event it is necessary to search for documents that speak about that event in a consensual way. For this reason, we can see that the conclusions related to historical events are limited to the subjective evaluation that will vary according to the judgment of each person.

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How many moles of copper atoms are in 150g of copper metal
djyliett [7]
The answer to this question would be: 2.36 mol

To answer this question, you need to know the molecular weight of copper. Molecular weight determines how much the weight of 1 mol of a molecule has. Copper molecular weight about 63.5g/mol. Then, the amount of mol in 150g copper should be: 150g / (63.5g/mol)= 2.36 mol
3 0
3 years ago
The chemical formula for magnesium oxide is MgO. A chemist determined by measurements that 0.030 moles of magnesium oxide partic
tamaranim1 [39]

Answer:

1.209g of MgO participates

Explanation:

In this problem, we have 0.030 moles of MgO that participates in a particular reaction.

And we are asked to solve for the mass of MgO that participates, that means, we need to convert moles to grams.

To convert moles to grams we need to use molar mass of the compound:

<em>1 atom of Mg has a molar mass of 24.3g/mol</em>

<em>1 atom of O has a molar mass of 16g/mol</em>

<em />

That means molar mass of MgO is 24.3g/mol + 16g/mol = 40.3g/mol

And mass of 0.030 moles of MgO is:

0.030 moles MgO * (40.3g/mol) =

<h3>1.209g of MgO participates</h3>
3 0
3 years ago
An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted to a total solution volume of 2.00 L. Calculate the molarity, mola
Sonja [21]

Answer:

The molarity is 0.359\frac{moles}{L}

The molality is 0.354 \frac{moles}{kg}

The mass percent of the solution es 3.45%

Explanation:

Molarity is a unit of concentration that indicates the amount of moles of solute that appear dissolved in each liter of the mixture. It is determined by:

Molarity (M)=\frac{number of moles of solute}{volume}

Being:

  • K: 39 g/mole
  • N: 14 g/mole
  • O: 16 g/mole

The molar mass of KNO₃ is:

KNO₃=  39 g/mole + 14 g/mole + 3*16 g/mole= 101 g/mole

You can apply the following rule of three: if 101 grams of KNO₃ are present in 1 mole, 72.5 grams in how many moles are present?

moles of KNO_{3}=\frac{72.5 grams*1 mole}{101 grams}

moles of KNO₃= 0.718

So you have:

  • moles of KNO₃= 0.718
  • volume= 2 L

Applying this quantity in the definition of molarity:

molarity=\frac{0.718 moles}{2 L}

Molarity= 0.359\frac{moles}{L}

<u><em>The molarity is 0.359</em></u>\frac{moles}{L}<u><em></em></u>

Molality is a way of measuring the concentration of solute in solvent and indicates the amount of moles of solute in each kilogram of solvent.

Then the molality is calculated by:

Molality=\frac{moles of solute}{mass of solvent in kilograms}

Density is defined as the property that matter, whether solid, liquid or gas, has to compress in a given space. That is, it is the amount of mass per unit volume. So, if the density of 1.05 g / mL for the solution indicates that in 1 mL of solution there are 1.05 grams of solution, in 2000 mL (where 2L = 2000 mL, because 1 L = 1000mL) how much mass is there?

mass=\frac{2000 mL*1.05 grams}{1 mL}

mass= 2100 grams

Since mass solution = mass water + mass KNO₃

then mass water = mass solution - mass KNO₃

Being mass solution 2100 grams and mass KNO₃ 72.5 grams, and replacing you get: mass water= 2100 grams - 72.5 grams

mass water= 2,027.5 grams

Then, being:

  • moles of KNO₃= 0.718
  • mass of solvent in kilograms= 2.0275 kg (being 2,027.5 grams= 2.0275 kilograms because 1,000 grams= 1 kilogram)

Replacing in the definition of molality:

molality=\frac{0.718 moles}{2.0275 kg}

molality= 0.354 \frac{moles}{kg}

<u><em>The molality is 0.354 </em></u>\frac{moles}{kg}<u><em></em></u>

The mass percent of a solution is the number of grams of solute per 100 grams of solution. Then the mass percent is the mass of the element or solute divided by the mass of the compound or solute and the result of which is multiplied by 100 to give a percentage.

mass percent=\frac{mass of solute}{mass of solution} *100

So, in this case:

mass percent=\frac{72.5 grams}{2100 grams} *100

mass percent= 3.45 % KNO₃ by mass

<u><em>The mass percent of the solution es 3.45%</em></u>

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