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3 years ago

What's difference between "formula unit" and "molecule" ?

1 answer:

6 0

The difference between "formula unit" and "molecule" lies in the fact that a molecule is made up of two or more elements that are bonded covalently while a formula nit represents the lowest whole number ratio of ions in an ionic compound which makes it applicable only to ionic substances.

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What is the percent composition of nitrogen in a 2.57 g sample of Al(NO3)3?

Lisa [10]

Answer:

19.8% of Nitrogen

Explanation:

In the Al(NO₃)₃ there are:

1 atom of Al

3 atoms of N

And 9 atoms of O

The molar mass of Al(NO₃)₃ is:

1 Al * (26.98g/mol) = 26.98g/mol

3 N * (14g/mol) = 42g/mol

9 O * (16g/mol) = 144g/mol

26.98 + 42 + 144 = 212.98g/mol

We can do a conversion using these molar masses to find the mass of nitrogen is the sample, that is:

2.57g * (42g/mol / 212.98g/mol) =

0.51g N

Percent composition of nitrogen is:

0.51g N / 2.57g * 100

= 19.8% of Nitrogen

6 0

2 years ago

Water has a boiling point of 100.0°C and a Kb of 0.512°C/m. What is the boiling

Reil [10]

Answer:

The boiling point of a 8.5 m solution of Mg3(PO4)2 in water is 394.91 K.

Explanation:

The formula for molal boiling Point elevation is :

$\Delta T_{b} = iK_{b}m$

$\Delta T_{b}$ = elevation in boiling Point

$K_{b}$ = Boiling point constant( ebullioscopic constant)

m = molality of the solution

i = Van't Hoff Factor

Van't Hoff Factor = It takes into accounts,The abnormal values of Temperature change due to association and dissociation .

In solution Mg3(PO4)2 dissociates as follow :

$Mg_{3}(PO_{4})_{2}\rightarrow 3Mg^{2+} + 2 PO_{4}^{3-}$

Total ions after dissociation in solution :

= 3 ions of Mg + 2 ions of phosphate

Total ions = 5

i = Van't Hoff Factor = 5

m = 8.5 m

$K_{b}$ = 0.512 °C/m

Insert the values and calculate temperature change:

$\Delta T_{b} = iK_{b}m$

$\Delta T_{b} = 5\times 0.512\times 8.5$

$\Delta T_{b} = 21.76 K$

Boiling point of pure water = 100°C = 273.15 +100 = 373.15 K

$\Delta T_{b} = T_{b} - T_{b}_{pure}$

$T_{b}_{pure}$ = 373.15 K[/tex]

21.76 = T - 373.15

T = 373.15 + 21.76

T =394.91 K

8 0

3 years ago

When baking cookies, what is one chemical change that takes place?

Alexus [3.1K]

Answer:

A. chocolate chips melting

Explanation:

It is a chemical change. cookies will soften and melt slightly as the cookies bake. the change is solid to liquid.

6 0

2 years ago

Read 2 more answers

What is the Scientific Method?

Doss [256]

Answer:

I just finished a unit on Scientific Method in my science class! Anyway, it's defined in the screenshots below. Hope this helps!

8 0

3 years ago

Why is a typical car battery in a car is filled with a solution of sulferic acid

Lesechka [4]

Answer:

Sulfuric acid has a higher density than water, which causes the acid formed at the plates during charging to flow downward and collect at the bottom of the battery.

8 0

3 years ago