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emmasim [6.3K]
4 years ago
5

What number should be substituted for the question mark to balance the equation and why is that the correct number?

Physics
2 answers:
grigory [225]4 years ago
6 0
The combustion of ethane results in the balanced equation 2C2H6 + 7O2 -> 4CO2 + H2O + energy because we see that after the combustion, the reactants have 8 + 6 = 14 Oxygen atoms in total (8 from 4CO2, 6 from 6H2O). Therefore, since there are 2 atoms of Oxygen in oxygen gas, we have 7O2 molecules in the beginning to hold the ratio true.
sergeinik [125]4 years ago
6 0
To balance an equation, we need to make sure the amount of atoms on the reactants and the products. 

How much oxygen's are on the reactants side? 

Lets count, 4*2 = 8  and 6, so 8+6 = 14

Now, start to predict the number. 

14/2 = 7

Answer: 7 is the correct answer
You might be interested in
If an object has a mass of 26 g on earth would its mass be less than 26 g on the moon
aleksley [76]

Answer:

No

Explanation:

No matter where an object is, its mass will stay the same, but its weight might change depending on gravity.

8 0
3 years ago
A Russian athlete lifts 300kg to a height of 2.5 m in 2 seconds. What is the work done? And what power is exerted?
snow_tiger [21]
We want to find the work done and power exerted, let’s start with work first.

We know that the equation for work is: W = F * D. We need to find the force which we can find by using: F = M * A.

Mass: 300kg
Acceleration (using equation from photo): 1.25 m/s^2

(The equation says x but can be used with y values)

If you are confused about how I found the acceleration; I plugged in 2.5 for the final y value, 0 for the initial y value, 0 for the initial velocity and 4 for t squared.

To solve, for acceleration it’s a matter of simple algebra. You can subtract the initial y position and the initial velocity from the final y position because they are 0. This leaves you with 2.5 m = 1/2a * t^2, from here I multiplied 2.5 by 2 to get rid of the 1/2. Now I have 5 = a * t^2. T^2 is just 2 squared, so four. Simply divide 5 by 4, and boom, you get 1.25 m/s^2.

Force = 300 kg * 1.25 m/s^2 = 375 Newtons

So, work = 500 N * 2.5 m = 1000 Joules

Power: W/t

So, Power = 1000 J / 2 seconds = 500 Watts

Hope this helps!

5 0
3 years ago
5. How fast does a 50 gram arrow need to travel to have 40 Joules of kinetic energy?​
qwelly [4]

Answer: v = 40 m/5

Explanation:

40 J = 1/2 (105) v^2

1600 = v^2

v = 40 m/5

7 0
3 years ago
A machinist with normal vision has a near point at 25 cm. The machinist wears eyeglasses in order to do close work. The power of
Alik [6]

Answer:

17.4 cm

Explanation:

Power of lens = +1.75 diopters

Focal length of lens

f=\frac{100}{1.75}=\frac{400}{7}

This is a convex lens as focal the diopter given is positive which makes the focal length positive. Image distance will be negative.

v = -25

\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\\\Rightarrow \frac{1}{-25}-\frac{1}{u}=\frac{1}{\frac{400}{7}}\\\Rightarrow -\frac{1}{u}=\frac{7}{400}+\frac{1}{25}\\\Rightarrow \frac{1}{u}=-\frac{7}{400}-\frac{1}{25}\\\Rightarrow \frac{1}{u}=-0.0575\\\Rightarrow u=-17.4\ cm

∴ The new near point is 17.4 cm

7 0
3 years ago
Jenna rides her scooter at a constant speed for 6 km. That part of her ride takes her 1 h. She then
AfilCa [17]

Answer:

5km/h

Explanation:

The equation for average speed is

Vavg = Δd/Δt

where Δd is distance and Δt is time

from what's given, we know she travelled 15km in total and the trip took 3 hours in total. We can now plug in the values into the equation

Vavg = 15/3

Vavg = 5km/h

4 0
3 years ago
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