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3 years ago

Which of the substances are elements please help

Chemistry

1 answer:

ivanzaharov [21]3 years ago

6 0

Answer:

Substances 1 and 2

Explanation:

an element only has 1 kind of atoms :3

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When would scientists need to change a theory?

Artyom0805 [142]

Answer:

if it cannot be made to fit the new findings

3 0

3 years ago

Read 2 more answers

Given the molar absorptivity for a species X of 1600 M-1cm-1 at a wavelength of 270 nm, and 400 M-1cm-1 at a wavelength of 540 n

Andre45 [30]

Answer:

Explanation:

From the given information:

At wavelength = 270 nm

$\varepsilon x_1 = 1600 \ m^{-1} \ cm^{-1} \\ \\ \varepsilon y_1 = 200 \ m^{-1} \ cm^{-1}$

At 270 nm

Suppose x is said to be the solution for the concentration of x and y to be the solution for the concentration of y;

Then:

$\varepsilon x_1 \ l + \varepsilon y_1 \ l= 0.5 \\ \\ A = A_1 + A_2$

$1600 xl + 200 yl= 0.5$

Divide both sides by 200

$8xl + yl = \dfrac{0.5}{200}$

$8x + y = \dfrac{0.5}{200}l$

Use l = 1cm (i.e the standard length)

Then;

$8x + y = \dfrac{0.5}{200} ---- (1)$

$\varepsilon x_2 x \ l + \varepsilon y_2 y \ l= 0.5 \\ \\ 40 xl + 800 yl = 0.5$

$x + 20 y = \dfrac{0.5}{400 \ l}$

since l = 1

$x + 20 y = \dfrac{0.5}{400 \ } --- (2)$

Equating both (1) and (2) together, we have:

$8x + y - 8x - 160 y = \dfrac{0.5}{200} - \dfrac{0.5 \times 8}{400} \\ \\ \implies - 159 y = \dfrac{0.5}{200} ( 1 - \dfrac{8}{2}) \\ \\ -159 y = \dfrac{-0.5 \times 3}{200} \\ \\ 159 \ y = 0.0075 \\ \\ y = \dfrac{0.0075}{159} \\ \\ y = 0.00004716 \\ \\ y = 4.7 \times 10^{-5 } \ M$

3 0

3 years ago

4NH3(g) + 3O2(g) --> 2N2(g) + 6H2O(l)

slamgirl [31]

Answer:

the right answer is : d

Explanation:

Because temperature is a cinetic factor.

3 0

4 years ago

Bob rides his horse 52 km in 3 hours 15 minutes. What is his average speed in kilometers per hour?

laila [671]

I think the answer is 16.51

7 0

3 years ago

A car traveling north with a velocity of 30 m/sec slows down to a velocity of 10 m/sec

hoa [83]

Answer:

-2m/s/s

Explanation:

Acceleration = change in speed / change in time

Change in speed = final speed - initial speed

In this case the change in speed was 10m/s - 30m/s = -20m/s

And change in time was 10 sec (within 10 sec)

Therefore acceleration = -20/10 = -2m/s/s

The acceleration is negative because the car slowed down (decelerated essentially) and the unit for acceleration is meters per second per second because it is the change in speed per second.

Hope this helped!

4 0

4 years ago