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ioda
4 years ago
12

PLS HELP I NEED TO PASS THIS... In physical science lab, Kim and Dawn added small pieces of magnesium to hydrochloric acid. They

observed that bubbles formed, the test tube got hot, and the magnesium disappeared. What is a sign that a chemical reaction has taken place in this experiment?
Question 7 options:


A.odor


B.gas is produced


C.temperature decreased


D.magnesium appeared
Chemistry
1 answer:
Bond [772]4 years ago
8 0

B gas is produced is the answer.


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The pressure of a gas sample was measured to be 654 mmhg. What is the pressure in kpa? (1 atm = 1. 01325 × 10 5 pa)
Stels [109]

Taking into account the change of units, the pressure of the gas sample is 87.19 kPa.

<h3>What is rule of three</h3>

In first place, the rule of three is a way of solving problems of proportionality between three known values and an unknown value, establishing a relationship of proportionality between all of them.

That is, what is intended with it is to find the fourth term of a proportion knowing the other three.  

If the relationship between the magnitudes is direct, that is, when one magnitude increases, so does the other (or when one magnitude decreases, so does the other) , the direct rule of three must be applied.

To solve a direct rule of three, the following formula must be followed, being a, b and c known data and x the variable to be calculated:

a ⇒ b

c ⇒ x

So: c=\frac{cxb}{a}

<h3>Pressure</h3>

The direct rule of three is the rule applied in this case where there is a change of units.

To perform in this case the conversion of units, you must first know that:

  • 1 atm= 760 mmHg
  • 1 atm = 1. 01325×10⁵ Pa= 101325 Pa
  • 1 kPa= 1000 Pa

So, if 1 atm is 760 mmHg, how many atm equals 654 mmHg?

760 mmHg ⇒ 1 atm

654 mmHg ⇒ x

So: x=\frac{654 mmHgx1 atm}{760 mmHg}

Solving:

<u><em>x=0.86 atm</em></u>

Now, if 101325 Pa are 1 atm, how many Pa equals 0.86 atm?

1 atm ⇒ 101325 Pa

0.86 atm ⇒ x

So: x=\frac{0.86 atmx101325 Pa}{1 atm}

Solving:

<u><em>x= 87,192.83 Pa</em></u>

Finally, if 1 kPa is 1000 Pa, how many kPa equals 87,192.83 Pa?

1000 Pa ⇒ 1 kPa

87,192.83 Pa ⇒ x

So: x=\frac{87,192.83 Pax1 kPa}{1000 Pa}

Solving:

<u><em>x=87.19283 kPa≅ 87.19 kPa</em></u>

In summary, the pressure of the gas sample is 87.19 kPa.

Learn more with this example:

brainly.com/question/12482948

#SPJ12

5 0
2 years ago
Answer the following questions that relate to electrochemical reactions. (a) Under standard conditions at 25˚C, Zn(s) reacts wit
Elanso [62]

Answer:

0.48 V

Explanation:

Zn(s) ------------> Zn^2+(aq) + 2e. Oxidation half equation (-0.76V)

Co^2+(aq) + 2e-----------> Co(s). Reduction half equation (-0.28)

Zn(s) + Co^2+(aq) -------------> Zn^2+(aq) + Co(s) overall redox equation

Zinc is the anode while cobalt is the cathode.

E°cell= E°cathode - E°anode

E°cell= -0.28-(-0.76)= 0.48 V

7 0
4 years ago
Read 2 more answers
Value of Δ H ∘ rxn for the equation NH 3 ( g ) + 2 O 2 ( g ) ⟶ HNO3 ( g ) + H 2 O ( g )
koban [17]

Answer: - 894.6 kJ/mol.

Explanation:

Hess law is states that the changes in enthalpies in a chemical reactions is independent of the pathway between the initial and final states.

∆H is the change in the sum of the internal energy of a system.

We are to find the Value of ΔH°(rxn) for the equation:

NH3 (g) + 2 O2 (g) ⟶ HNO3 (g) + H2O (g). ----------------------------------(**).

From the series of equations given;

==> 4NH3 (g) + 5O2 (g) -------->4 NO(g) + 6H2O (l). ∆H = -1166.0 kJ/mol.--------------------------------------(1).

===> 2NO(g) + O2 (g) ------> 2NO2 (g). ∆H = -116.2 kJ/mol.---------------(2).

===> 3NO2 (g) + H2O (l) ---------> 2HNO3 (aq) + NO (g). ∆H = -137.3 kJ/mol.-------------------------------------(3).

The first thing to do is to multiply equation (2) by 3. Also, multiply equation (3) by 2. This will give us equation (4) and (5) respectively.

6NO + 3 O2 ----------------> 6NO2. ∆H= 3 × (-116.2 kJ/mol) = -348.6 kJ/mol. ------------------------------------(4).

6NO2 + 2 H2O ----------------> 4HNO3 + 2 NO. ∆H= 2 × (-137.3kj/mol) = -274.6 kJ/mol ---------------------------(5).

Next, add equations (4) and (5) to give;

4NO +3O2 +2H2O -------------> 4HNO3. ∆H = -623.2 kJ/mol. -----(6).

Add this equation to the equation (1) from above, we have;

4NH3 + 8O2 --------------> 4HNO3 + 4H2O. ∆H= -1789.2 kJ/mol. --------(7).

Then, divide the equation (7) above by 2 to give us back the equation (**).

NH3 (g) + 2 O2 (g) ⟶ HNO3 (g) + H2O (g). ∆H= -894.6 kJ/mol.

Δ H^∘ (rxn)= - 894.6 kJ/mol.

5 0
3 years ago
Liquid octane (CH) has a density of 0.7025 g/mL at 20 °C. Find the true mass (murue) of octane when the mass weighed in 18 air i
Goshia [24]

Explanation:

According to Buoyance equation,

          m = [m' \times \frac{1 - \frac{d_{a}}{d_{w}}}{1 - \frac{d_{a}}{d}}]

where,      m = true mass

                 m' = mass read from the balance = 17.320 g

              d_{a} = density of air = 0.0012 g/ml

              d_{w} = density of the balance = 7.5 g/ml

                    d = density of liquid octane = 0.7025 g/ml

Now, putting all the given values into the above formula and calculate the true mass as follows.

      m = [m' \times \frac{1 - \frac{d_{a}}{d_{w}}}{1 - \frac{d_{a}}{d}}]    

          = [17.320 g \times \frac{1 - \frac{0.0012 g/ml}{7.5 g/ml}}{1 - \frac{0.0012 g/ml}{0.7025}}]

          = 17.320 g \times 0.999850                

          = 17.317 g

Thus, we can conclude that the true mass of octane is 17.317 g.

7 0
3 years ago
Write one word for the following short form of an element​
ra1l [238]

Answer:

symbol?

Explanation:

6 0
3 years ago
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