When a bond is created how many valence electrons are needed to fill an octet?

What information does the fossil record provide?

lukranit [14]

By studying the fossil record we can tell how long life has existed on Earth, and how different plants and animals are related to each other. Often we can work out how and where they lived, and use this information to find out about ancient environments. Fossils can tell us a lot about the past.

6 0

3 years ago

A gas is produced when 25 g of substance X is mixed into 60 g of solution Z in a beaker. The mass of the solution in the beaker

Zepler [3.9K]

mass of the gas = 10 g

<h3>Further explanation</h3>

<em>The law of conservation of mass :</em>

<em>In a closed / isolated system, the total mass of the substance before the reaction will be equal to the total mass of the reaction product.</em>

Reaction

$\tt X+Z\rightarrow gas+solution$

mass before reaction=mass after reaction

$\tt 25+60=gas+75\\\\gas=25+60-75=10~g$

5 0

3 years ago

Given that naphthalene is insoluble in water and sublimes easily upon heating, describe two different methods by which you could

Sunny_sXe [5.5K]

<span>Based on solubilities you can separate naphthalene and NaCl by adding the mixture to a volume of water. NaCl is highly soluble in water, so it will dissolve completely, while the insoluble naphthalen will remain solid. Next your filter the solution, washing the solid with pure water to eliminate all the NaCl from it. The NaCl will remain is solution, and you can obtain it by evaporating the water. The other method to separate naphthalene and NaCl is based on sublimation property of naphthalene: you can permit that naphthalene sublimes freely or use vacuum to accelerate the process. You use a closed vessel to catch all the gas, while the NaCl will remain solid.</span>

3 0

4 years ago

Which is NOT an application of chemistry to life? *

rodikova [14]

I’m pretty sure it’s D

4 0

3 years ago

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl?0.09600.4720.1064.44

Tresset [83]

Answer:

mole fraction of LiCl = 0.096

Explanation:

Weight percentage -

weight percentage of A is given as , the weight of the substance A by weight of the total solution multiplied by 100 .

i.e.

weight % A = weight of A / weight of solution * 100

GIven ,

20.0 wt% LiCl

Now ,

Assuming weight of solution = 100 g ,

weight if LiCl = 20.0 g

Since ,

Moles is denoted by given mass divided by the molecular mass ,

Hence ,

n = w / m

n = moles ,

w = given mass ,

m = molecular mass .

From the question ,

molar mass of LiCl = 42.39 g/mol

moles of LiCl = mass / molar mass = 20.0 g / 42.39 g/mol = 0.472 mol

Since , solution = 100 g ,

and ,

Solution = solute + solvent

100g = 20g + solvent

Solvent = 80 g

mass of water = 80 g

water molecular mass = 18 g/mol

moles of water = 80g / 18 g/mol = 4.44 mol

Mole fraction -

It is the ratio of the moles of one of the component of the solution by the mole of the solution .

Total moles of the solution = moles of the solute + moles of solvent

Total moles of the solution = 0.472 mol + 4.44 mol = 4.92 mol

Now ,

mole fraction of LiCl = moles of LiCl / total moles = 0.472 mol / 4.92

mole fraction of LiCl = 0.096

3 0

3 years ago