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3 years ago

Why must sample spots be above the solvent in paper chromatography

1 answer:

6 0

Because if they are submerged in the solvent, they would dissolve! This would prevent them from seperating and not allow you to actually record anything

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The road map in the text shows that to convert from one unit to another, you must use the ____ as an intermediate step. ___ conv

jonny [76]

Answer:

Conversion factor;

Molar mass;

Avogadro's constant and molar mass

Explanation:

Firstly, an intermediate step is to define the conversion factor that will be then used in a conversion technique called dimensional analysis in order to convert from one unit to another. An example of a conversion factor would be, for example, 1 L = 1000 mL, which can be manipulated as a fraction, either $\frac{1 L}{1000 mL}$ or $\frac{1000 mL}{1 L}$ ;
Secondly, in order to convert mass to moles, we need to know the molar mass of a compound which has a units of g/mol (that is, it shows how many grams we have per 1 mole of substance.
Thirdly, Avogadro's constant, $N_A = 6.022\cdot 10^{23} mol^{-1}$ tells us that there is $N_A$ number of molecules or atoms in 1 mole of substance. We need two conversion factors to convert the number of molecules to a mass: firstly, we need to convert the number of molecules into the number of moles using Avogadro's constant and then we need to use the molar mass to convert the moles obtained into mass.

5 0

3 years ago

When calcium carbonate is added to hydrochloric acid, calcium chloride, carbon dioxide, and water are produced. CaCO 3 ( s ) + 2

e-lub [12.9K]

Answer: The mass of calcium chloride formed is 15.21 grams.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For calcium carbonate:

Given mass of calcium carbonate = 32.0 g

Molar mass of calcium carbonate = 100 g/mol

Putting values in equation 1, we get:

$\text{Moles of calcium carbonate}=\frac{32.0g}{100g/mol}=0.32mol$

For hydrochloric acid:

Given mass of hydrochloric acid = 10.0 g

Molar mass of hydrochloric acid = 36.5 g/mol

Putting values in equation 1, we get:

$\text{Moles of hydrochloric acid}=\frac{10.0g}{36.5g/mol}=0.274mol$

The given chemical equation follows:

$CaCO_3(s)+2HCl(aq.)\rightarrow CaCl_2(aq.)+H_2O(l)+CO_2(g)$

By Stoichiometry of the reaction:

2 moles of hydrochloric acid reacts with 1 mole of calcium carbonate

So, 0.274 moles of hydrochloric acid will react with = $\frac{1}{2}\times 0.274=0.137mol$ of calcium carbonate

As, given amount of calcium carbonate is more than the required amount. So, it is considered as an excess reagent.

Thus, hydrochloric acid is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

2 moles of hydrochloric acid produces 1 mole of calcium chloride.

So, 0.274 moles of hydrochloric acid will produce = $\frac{1}{2}\times 0.274=0.137moles$ of calcium chloride.

Now, calculating the mass of calcium chloride from equation 1, we get:

Molar mass of calcium chloride = 111 g/mol

Moles of calcium chloride = 0.137 moles

Putting values in equation 1, we get:

$0.137mol=\frac{\text{Mass of calcium chloride}}{111g/mol}\\\\\text{Mass of calcium chloride}=(0.137mol\times 111g/mol)=15.21g$

Hence, the mass of calcium chloride formed is 15.21 grams.

4 0

3 years ago

Maria formed when asteroids punctured the moon's surface ,allowing magma to bleed out and create?

dlinn [17]

The answer that best completes the statement above is EXTENSIVE LAVA FLOW. Maria is the name that refers to an asteroid family. And this has punctured the surface of the moon which created magma to bleed out and resulted in an extensive lava flow. Hope this answer helps.

5 0

3 years ago

Read 2 more answers

The table shows the properties of some organic compounds.

Shalnov [3]

Answer:

option C is correct

..............,

3 0

3 years ago

Which statement is NOT true about a scientific law?

jekas [21]

Answer:

Explanation:

6 0

3 years ago