1. A positive value for AH for a chemical reaction is an indication of which of the following?

Separate a mixture of sand, common salt, copper pieces and iron fillings. Also measure the amount of common salt in the mixture.

Neporo4naja [7]

Answer:

Explanation:

This question seeks to test the knowledge of separation techniques.

From the narration in the question, the first separation to be done is the removal of Iron fillings by the use of magnet (magnetic separation). Since Iron is magnetic, the iron fillings will be attracted by the magnet hence removing the iron fillings from the mixture.

The second constituent to be removed will be the copper pieces by the use of a sieve (sieving). Copper pieces have relatively larger sizes than sand and common salt, hence a sieve (which separates particles based on size) can be used to remove the copper pieces from the mixture.

What will be left in the mixture after the processes above will be salt and water. This mixture will have to be dissolved in water; the salt will dissolve in water while the sand will not. After which, filtration will be done to remove the sand which will be collected on the filter paper as filtride and the salt solution will pass through the filter paper as filtrate.

The salt solution can then be evaporated to dryness to retrieve the solid salt from the solution.

The amount of salt in the mixture can then be measured using a weighing balance.

Some of safety measures to be taken during the course of this experiment includes performing the experiment in an airtight and controlled environment. Lab coat and hand gloves should be worn during the course of the experiment. The evaporation to dryness should not be done close to an inflammable material/substance

5 0

3 years ago

A certain liquid has a normal boiling point of and a boiling point elevation constant . A solution is prepared by dissolving som

jek_recluse [69]

The question is incomplete, the complete question is:

A certain substance X has a normal freezing point of $-6.4^oC$ and a molal freezing point depression constant $K_f=3.96^oC.kg/mol$ . A solution is prepared by dissolving some glycine in 950. g of X. This solution freezes at $-13.6^oC$ . Calculate the mass of urea that was dissolved. Round your answer to 2 significant digits.

<u>Answer:</u> The mass of glycine that can be dissolved is $1.3\times 10^2g$

<u>Explanation:</u>

Depression in the freezing point is defined as the difference between the freezing point of the pure solvent and the freezing point of the solution.

The expression for the calculation of depression in freezing point is:

$\text{Freezing point of pure solvent}-\text{freezing point of solution}=i\times K_f\times m$

OR

$\text{Freezing point of pure solvent}=\text{Freezing point of solution}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times w_{solvent}\text{(in g)}}$ ......(1)

where,

Freezing point of pure solvent = $-6.4^oC$

Freezing point of solution = $-13.6^oC$

i = Vant Hoff factor = 1 (for non-electrolytes)

$K_f$ = freezing point depression constant = $3.96^oC/m$

$m_{solute}$ = Given mass of solute (glycine) = ?

$M_{solute}$ = Molar mass of solute (glycine) = 75.07 g/mol

$w_{solvent}$ = Mass of solvent = 950. g

Putting values in equation 1, we get:

$-6.4-(-13.6)=1\times 3.96\times \frac{m_{solute}\times 1000}{75.07\times 950}\\\\m_{solute}=\frac{7.2\times 75.07\times 950}{1\times 3.96\times 1000}\\\\m_{solute}=129.66g=1.3\times 10^2g$

Hence, the mass of glycine that can be dissolved is $1.3\times 10^2g$

5 0

2 years ago

What causes water to freeze solid when placed in the freezer

svet-max [94.6K]

Answer:

the molecules slow down and get more dense

Explanation:

you seem to slow down when its cold too...

5 0

3 years ago

Each of the two different solids A and B melts at 133 o C. A sample of an unknown solid melts around 133 o C, and is either A or

rusak2 [61]

Answer:

See explanation

Explanation:

The melting point range of a pure compound is about 1-2ºC of the expected melting point. An impure solid melts within a range that is both larger than that of the pure substance (>1ºC) and begin at a lower temperature because impurities decrease the meting point. A melting range of 5º or more indicates that a compound is impure.

Since the melting points of A and B are estimated at 133 o C, the melting point range for each pure substance must be slightly different from each other. The melting point of the unknown is measured and its range is compared with the melting point ranges of pure A and B then decision can now be made about the identity of the unknown solid.

4 0

3 years ago

How many atoms of fluorine are in 5.6x10^22 molecules of MgF2

bija089 [108]

Answer:

1.12x10²³ atoms of F

Explanation:

A molecule is a group of 2 or 3 atoms that are bonded by electrostatic charges.

In 1 molecule of MgF2 there are 2 atoms of fluorine and 1 atom of magnesium.

Thus, there are 2 atoms of fluorine per molecule of MgF2. In 5.6x10²² molecules:

5.6x10²² molecules MgF2 * (2 atoms Fluorine / 1 molecule MgF2) =

<h3>1.12x10²³ atoms of F</h3>

7 0

3 years ago