How did early scientists attempt to organize the elements

A plane flying against the wind covers the 900-kilometer distance between two aerodromes in 2 hours. The same plane flying with

Mashcka [7]

Answer:

The speed of the wind is 25 km/hr.

Explanation:

Let us call $v_p$ the speed of the plane and $v_w$ the speed of the wind. When the plane is flying against the wind, it covers the distance of 900-km in 2 hours (120 minutes); therefore;

(1). $v_p - v_w = \dfrac{900km}{120min}$

And when the plane is flying with the wind, it covers the same distance in 1 hour 48 minutes (108 minutes)

(2). $v_p+v_w= \dfrac{900km}{108min}$

From equation (1) we solve for $v_p$ and get:

$v_p = \dfrac{900km}{120min}+v_w$ ,

and by putting this into equation (2) we get:

$\dfrac{900km}{120min}+v_w+v_w= \dfrac{900km}{108min}$

$2v_w= \dfrac{900km}{108min}-\dfrac{900km}{120min}$

$2v_w = 8.3km/min - 7.5km/min$

$2v_w = 0.83km/min$

$v_w = 0.4165km/min$

or in km/hr this is

$\boxed{v_w= 25km/hr }$

4 0

3 years ago

Select the best statement

s2008m [1.1K]

The correct answer is B. hopes this help

5 0

4 years ago

xConsider the following reduction potentials: Cu2+ + 2e– Cu E° = 0.339 V Pb2+ + 2e– Pb E° = –0.130 V For a galvanic cell employi

slega [8]

Answer:

Approximately $\rm 90\; kJ$ .

Explanation:

Cathode is where reduction takes place and anode is where oxidation takes place. The potential of a electrochemical reaction ( $E^{\circ}(\text{cell})$ ) is equal to

$E^{\circ}(\text{cell}) = E^{\circ}(\text{cathode}) - E^{\circ}(\text{anode})$ .

There are two half-reactions in this question. $\rm Cu^{2+} + 2\,e^{-} \rightleftharpoons Cu$ and $\rm Pb^{2+} + 2\,e^{-} \rightleftharpoons Pb$ . Either could be the cathode (while the other acts as the anode.) However, for the reaction to be spontaneous, the value of $E^{\circ}(\text{cell})$ should be positive.

In this case, $E^{\circ}(\text{cell})$ is positive only if $\rm Cu^{2+} + 2\,e^{-} \rightleftharpoons Cu$ is the reaction takes place at the cathode. The net reaction would be

$\rm Cu^{2+} + Pb \to Cu + Pb^{2+}$ .

Its cell potential would be equal to $0.339 - (-0.130) = \rm 0.469\; V$ .

The maximum amount of electrical energy possible (under standard conditions) is equal to the free energy of this reaction:

$\Delta G^{\circ} = n \cdot F \cdot E^{\circ} (\text{cell})$ ,

where

$n$ is the number moles of electrons transferred for each mole of the reaction. In this case the value of $n$ is $2$ as in the half-reactions.
$F$ is Faraday's Constant (approximately $96485.33212\; \rm C \cdot mol^{-1}$ .)

$\begin{aligned}\Delta G^{\circ} &= n \cdot F \cdot E^{\circ} (\text{cell})\cr &= 2\times 96485.33212 \times (0.339 - (-0.130)) \cr &\approx 9.0 \times 10^{4} \; \rm J \cr &= 90\; \rm kJ\end{aligned}$ .

5 0

3 years ago

A 2 column by 3 row table. Column 1 is titled Planet A with the following entries: Atmosphere is mostly carbon dioxide, Surface

Eddi Din [679]

Answer: earth

Explanation: isn’t earth the only plant with LIQUID water?

4 0

3 years ago

The express train can travel 100 miles per hour. This information describes the train'sAnsweracceleration.direction.speed.veloci

solmaris [256]

Velocity because it gives the displacement and time

3 0

4 years ago