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3 years ago

Why is a solution of 4% acetic acid in 95% ethanol used to wash the crude aldol-dehydration product?

1 answer:

5 0

A cold acetic acid solution is used to wash the residue of the reagent in preparation of an aldol condensation product after vacuum filtration. The main reason in washing with the acetic acid rinse is to neutralize any sodium hydroxide.

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I need help please

densk [106]

Answer:

PLIS HELP PLSI PLSI PLIS

k 8987 pjbh hub hyujbnbj

4 0

3 years ago

a 5. A bar has a 20 N weight at one end. You have a weight of 15 N to hang somewhere on the bar so that the bar is in equilibriu

Dmitry_Shevchenko [17]

the answer is a

Explanation:

it's a because 5n time 4 will give u 20n

5 0

2 years ago

When a wave hits a boundary, what determines how much is reflected and refracted?

Dafna1 [17]

Answer:

Angle and speed of wave

Explanation:

The two phenomena involved here are:

- Reflection: reflection occurs when a light wave bounces off the interface between two mediums, returning into the first medium, at a different angle

- Refraction: refraction occurs when a light wave passes through the interface between the two mediums, passing into the second medium, changing direction and speed

The coefficient of reflection tells what is the fraction of the wave that is reflected over the total; it is calculated as

$R=|\frac{n_1 cos \theta_1 - n_2 cos \theta_2}{n_1 cos \theta_1 + n_2 cos \theta_2}|^2$

where

$n_1, n_2$ are the index of refraction of the 1st and 2nd medium

$\theta_1, \theta_2$ are the angle between the ray of light and the normal to the interface in the 1st and 2nd medium

From the formula, we see that the % of wave that is reflected depends on the angle and the index of refraction. Moreover, the index of refraction is related to the speed of the wave by:

$n=\frac{c}{v}$

where c is the speed of light in a vacuum and v the speed of light in the medium; therefore, the correct answer is

Angle and speed of wave

5 0

3 years ago

An 80-kg quarterback jumps straight up in the air right before throwing a 0.43-kg football horizontally at 15 m/s . How fast wil

Oksanka [162]

Answer:

vBxf = 0.08625m/s

Explanation:

This is a problem about the momentum conservation law. The total momentum before equals the total momentum after.

$p_f=p_i$

pf: final momentum

pi: initial momentum

The analysis of the momentum conservation is about a horizontal momentum (x axis). When the quarterback jumps straight up, his horizontal momentum is zero. Then, after the quarterback throw the ball the sum of the momentum of both quarterback and ball must be zero.

Then, you have:

$m_Qv_{Qxi}+m_{Bxi}v_{Bxi}=m_Qv_{Qxf}+m_{Bxf}v_{Bxf}$ (1)

mQ: the mass of the quarterback = 80kg

mB: the mass of the football = 0.43kg

(vQx)i: the horizontal velocity of quarterback before throwing the ball = 0m/s

(vBx)i: the horizontal velocity of football before being thrown = 0m/s

(vQx)f: the horizontal velocity of quarterback after throwing the ball = ?

(vBx)f: the horizontal velocity of football after being thrown = 15 m/s

You replace the values of the variables in the equation (1), and you solve for (vBx)f:

$0\ kgm/s=-(80kg)(v_{Bxf})+(0.46kg)(15m/s)\\\\v_{Bxf}=\frac{(0.46kg)(15m/s)}{80kg}=0.08625\frac{m}{s}$

Where you have taken the speed of the quarterback as negative because is in the negative direction of the x axis.

Hence, the speed of the quarterback after he throws the ball is 0.08625m/s

6 0

4 years ago

The speed of light is 3 x 10^8 m/s. If its frequency is 4.11 x 10^4 Hz, what is its wavelength?

spin [16.1K]

Answer:

21'8

Explanation:

5 0

3 years ago