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san4es73 [151]
3 years ago
14

What are the four important steps needed to obtain accurate melting points on a mel-temp

Chemistry
1 answer:
AveGali [126]3 years ago
3 0

Explanation:

1) refine the specimen into fine powder 2) place the smallest amount you can see in the capillary tube 3) set the voltage to increase exponentially to 200 below the predicted temperature, then adjust so that the temperature rises to 20 per minute 4) report the temperature at which the liquid first appears and the temperature at which the last crystal disappears.

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The maximum allowable concentration of pb2+ ions in drinking water is 0.05 ppm (i.e., 0.05 g of pb2+ in 1 million grams of water
trasher [3.6K]
PbSO₄ partially dissociates in water. the balanced equation is;
                    
                       PbSO₄(s) ⇄  Pb²⁺(aq) + SO₄²⁻(aq)
Initial                                     -                -
Change             -X               +X           +X
Equilibrium                           X              X

Ksp           =    [Pb²⁺(aq)] [SO₄²⁻(aq)]
1.6 x 10⁻⁸  =    X * X
1.6 x 10⁻⁸  =    X²
          X    =   1.3 x 10⁻⁴ M
      
Hence the Pb²⁺ concentration in underground water is 1.3 x 10⁻⁴ M. 
[Pb²⁺]  = 1.3 x 10⁻⁴ M.
           = 1.3 x 10⁻⁴ mol / L x 207 g / mol 
           = 26.91 ppm

8 0
3 years ago
Which statement is a valid conclusion about the activation energy of the reverse reaction if the forward reaction is exothermic?
babunello [35]

Answer:

e) The activation energy of the reverse reaction is greater than that of the forward reaction.

Explanation:

  • Activation energy is the minimum amount of energy that is required by the reactants to start a reaction.
  • An exothermic reaction is a reaction that releases heat energy to the surrounding while an endothermic reactions is a reaction that absorbs heat from the surrounding.
  • <em><u>In reversible reactions, when the forward reaction is exothermic it means the reverse reaction will be endothermic, therefore the reverse reaction will have a higher activation energy than the forward reaction.</u></em> The activation energy of the reverse reaction will be the sum of the enthalpy and the activation energy of the forward reaction.
4 0
3 years ago
Use wedge-bond perspective drawings (if necessary) to sketch the atom positions in a general molecule of formula (not shape clas
yuradex [85]

The atom positions in a general molecule of formula (not shape class) AXn that has shape square pyramidal at the corers of square and one at the above center of the square.

<h3>What is square pyramidal?</h3>

The square pyramidal is a shape geometry of the hybridization in which it consists of one lone pair and 5 bond pairs of electrons that repel each other and due to which the geometry changes from octahedral to square pyramidal.

As atoms are located at the four corners of the planer and one atom at the above center of the planner which is repelled by 4 atoms present at the corner of the planer.

Therefore, the atom positions in a general molecule of formula (not shape class) AXn that has a shape square pyramidal at the corners of the square and one at the above center of the square.

Learn more about square pyramidal, here;

brainly.com/question/8742529

#SPJ4

7 0
1 year ago
. Un cuerpo irregular se introduce dentro de una probeta que inicialmente tiene un volumen de 20 ml como muestra la figura Despu
MrMuchimi

Answer:

El volumen del cuerpo es el mismo al comienzo de la experiencia.

Explicación:

El volumen del cuerpo es el mismo al principio porque el volumen no cambia si la temperatura permanece igual. Si cambiamos la temperatura i. mi. Al aumentar la temperatura, las moléculas comienzan a expandirse y se produce un aumento de volumen mientras que cuando disminuimos la temperatura, las moléculas de esa sustancia comienzan a contraerse y el volumen de esa sustancia disminuye. Entonces concluimos que el volumen depende de la temperatura.

6 0
2 years ago
When energy is transferred from the air to the water, what happens to most of the energy? A. It travels through the water. B. It
BigorU [14]

Answer: Option (A) is the correct answer.

Explanation:

When energy is transferred from the air to the water then energy is absorbed by the water molecules.

This energy travels through one molecule of water to another molecule of water by the process of convection.

Thus, we can conclude that when energy is transferred from the air to the water, then it travels through the water.

3 0
3 years ago
Read 2 more answers
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