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svet-max [94.6K]
3 years ago
11

What is the molality of an aqueous kbr solution with a mole fraction of kbr, x, equal to 0.245?

Chemistry
1 answer:
kompoz [17]3 years ago
4 0
Molality is used to express concentration and it is:
molality = moles of solvent / kilogram solution

Now, lets assume there is one mole of solution. Then, there will be 0.245 moles of KBr and 0.755 moles of water. We multiply these molar fractions with the substances' molar masses to find the weight of one mole of solution.

Weight of one mole of solution = 0.245 * 119 + 0.755 * 18
Weight = 42.74 grams

Converting this weight to kilograms, this is 0.043 kg. We now multiply the moles of KBr by the kilograms of solution to find the molality:

molality = 0.245 / 0.043

The molality of the solution is 5.70 moles per kg
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Determine the mass in grams of 4.69 x 1021 atoms of barium. (The
Virty [35]

Answer:

1.07 g Ba

Explanation:

Hello there!

In this case, according to the definition of the Avogadro's number and the molar mass, it is possible to say that 6.022x10^{23} atoms of barium equal one mole, and at the same time, 1 mole equals 137.327 grams of this element; thus, it is possible to say that 6.022x10^{23} atoms of barium have a mass of 137.327 grams; therefore, it i possible for us to calculate the required mass in grams as shown below:

4.69x10^{21}atoms*\frac{137.327gBa}{6.022x10^{23} atoms} \\\\=1.07gBa

Best regards!

5 0
3 years ago
68.3 grams of sodium hydroxide reacts with 78.3 grams of magnesium nitrate. ____ grams of magnesium hydroxide will form from thi
Vera_Pavlovna [14]

Answer:

30.8 grams of magnesium hydroxide will form from this reaction, and magnesium nitrate is the limiting reagent.

Explanation:

The reaction that takes place is:

  • 2NaOH + Mg(NO₃)₂ → 2NaNO₃ + Mg(OH)₂

Now we <u>convert the given masses of reactants to moles</u>, using their respective <em>molar masses</em>:

  • 68.3 g NaOH ÷ 40 g/mol = 1.71 mol NaOH
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0.528 moles of Mg(NO₃)₂ would react completely with (0.528 * 2) 1.056 moles of NaOH. There are more than enough NaOH moles, so NaOH is the reagent in excess and <em>Mg(NO₃)₂ is the limiting reagent.</em>

Now we <u>calculate how many Mg(OH)₂ are produced</u>, using the <em>moles of the limiting reagent</em>:

  • 0.528 mol Mg(NO₃)₂ * \frac{1molMg(OH)_2}{1molMg(NO_3)_2} = 0.528 mol Mg(OH)₂

Finally we convert Mg(OH)₂ moles to grams:

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7 0
3 years ago
1.Which statement best describes scientific laws
gtnhenbr [62]
In a way, all of the answers could be argued for (for example: in the first option: if the scientists' opinions are understood to be "informed understanding of the causes of events"), but one of the options is the best:
Scientific laws describe specific relationships in nature without offering
an explanation.

The reason why  I think this is true is that many laws are phased too short and too concise to provide comprehensive explanations, instead they describe the relationships that must hold.


One of the options is pplain false:
Scientific laws explain why natural events occur. -"Scientific laws were theories that have been tested, proven, and adopted as laws." - since they are not adopted as laws. 



6 0
3 years ago
According to Hess’s law, if a series of intermediate reactions are combined, the enthalpy change of the overall reaction is
sdas [7]
I think the answer is B. the sum of the enthalpy changes of the intermidiate reactions
4 0
3 years ago
Read 2 more answers
Draw conclusion: The density of water is 1.0 g/mL, or 1.0 g/cm². Look at the data in your table. How can you use the density of
ANEK [815]

Answer:

work out if it's either going to sink or float

Explanation:

this can be carried out by calculating the numbers

3 0
3 years ago
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