Assume that you have to prepare a 200 g salt solution, and the concentration must be 15 % by mass. How many grams of solute and water you must mix together.

170 g

Explanation:

w/w% concentration = mass of solute/ mass of solution * 100

mass of solute = x

mass of solution = 200 g

w/w% concentration =  15 % by mass

15 = x/200 * 100

15 = 100x/200

200 * 15 = 100x

x = 200 * 15/100

x = 2 * 15

x = 30g

But mass of solution = mass of solute + mass of solvent

mass of solute = 30g

mass of solvent = mass of solution  - mass of solute

mass of solvent = 200 g - 30 g

mass of solvent = 170 g

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j

1.solid

2.carbon dioxide

3.helium