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3 years ago

How do u find which is physical or chemical changes

Chemistry

1 answer:

zhenek [66]3 years ago

5 0

Physical change can return back to its original form while a chemical change cannot

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The book procedure calls for 2,5-dimethylhexane-2,5-diol and concentrated hydrochloric acid to be shaken in a reaction vial. Whi

san4es73 [151]

Answer:

E) All of the above.

Explanation:

Hello,

Since the acidic nature of the HCl implies its corrosiveness, when it is in contact with the skin and eyes the burning starts immediately, so gloves and goggles must be worn. Next, the fuming hydrochloric acid (37% by mass) is volatile so it gives off even when dissolved into water, so it must be used in the fume hood. Then, since vapors are produced during the chemical reaction, an overpressure could be attained, that's why we must keep the glass sash of the fume hood between us and the vial. As a common risk, the vial could be dropped causing the hydrochloric acid to splash, so we must keep the vial well inside the hood.

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7 0

3 years ago

What solid element is black, is an electrical conductor, is brittle and is found in group 4 of the periodic table?

elixir [45]

Answer: silicon Si, Germanium GE

Explanation:

4 0

3 years ago

Describe the difference between an independent and dependent valuable?

kolbaska11 [484]

Answer:

A dependent valuable is a valuable whose variation depend on another variable usually the independent variable. An independent variable is a variable whose variation do not depend on another variable but the reseacher experimenting.

7 0

4 years ago

The solubility of oxygen gas in water at 40 ∘c is 1.0 mmol/l of solution. What is this concentration in units of mole fraction?

juin [17]

The formula for mole fraction is:

$mole fraction of solute = \frac{number of moles of solute}{total number of moles of solution}$ -(1)

The solubility of oxygen gas = 1.0 mmol/L (given)

1.0 mmol/L means 1.0 mmol are present in 1 L.

Converting mmol to mol:

$1.00 mmol\times \frac{1 mol}{1000 mmol} = 0.001 mol$

So, moles of oxygen = 0.001 mol

For moles of water:

1 L of water = 1000 mL of water

Since, the density of water is 1.0 g/mL.

$Density = \frac{mass}{volume}$

$Mass = 1.0 g/ml\times 1000 mL = 1000 g$

So, the mass of water is 1000 g.

Molar mass of water = 18 g/mol.

Number of moles of water = $\frac{1000 g}{18 g/mol} = 55.55 mol$

Substituting the values in formula (1):

$mole fraction = \frac{0.001}{55.55+0.001}$

$mole fraction = 1.8\times 10^{-5}$

Hence, the mole fraction is $1.8\times 10^{-5}$ .

7 0

3 years ago

How many kj of heat are needed to completely melt 32.3 g of h2o, given that the water is at its melting point? the heat of fusio

timurjin [86]

Answer: fourth option, 10.8 kJ

Explanation:

The heat of fusion, also named latent heat of fusion, is the amount of heat energy required to change the state of a substance from solid to liquid (at constant pressure).

The data of the heat of fusions of the substances are reported in tables and they can be shown either per mole or per gram of substance.

In this case we have that the heat of fusion for water is reported per mole: 6.02 kJ/mole.

The formula to calculate how many kJ of heat (total heat) are needed to completely melt 32.3 g of water, given that the water is at its melting point is:

Heat = number of moles × heat of fusion

The calculations are:

number of moles = mass / molar mass

number of moles = 32.3 g / 18.015 g/mol = 1.79 mol

Heat = 1.79 mol × 6.02 kJ / mol = 10.8 kJ ← answer

5 0

3 years ago

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