1. An isotope has the same ________, but a different _______

A coffee cup calorimeter is prepared, containing 100.000 g of water (specific heat capacity = 4.184 J/g K) at initial temperatur

BARSIC [14]

Answer : The molar heat of solution for the salt is 452.9 kJ/mole

Explanation :

First we have to calculate the heat of solution.

$q=m\times c\times \Delta T$

where,

q = heat of solution = ?

c = specific heat of water = specific heat of solution = $4.184J/g.K=4.184J/g^oC$

m = mass of solution = 107.093 g

Mass of solution = Mass of water + Mass of salt
Mass of solution = 100.000 g + 7.093 g = 107.093 g

$\Delta T$ = change in temperature = $T_2-T_1=(80.000-61.128)=18.872^oC=$

Now put all the given values in the above formula, we get:

$q=107.093g\times 4.184J/g^oC\times 18.872^oC$

$q=8456.111J=8.456kJ$

Now we have to calculate the molar heat of solution for the salt, in kJ/mol.

$\Delta H=\frac{q}{n}$

where,

$\Delta H$ = molar heat of solution = ?

q = heat required = 8.456 kJ

m = mass of salt = 7.093 g

Molar mass of salt = 379.984 g/mol

$\text{Moles of salt}=\frac{\text{Mass of salt}}{\text{Molar mass of salt}}=\frac{7.093g}{379.984g/mole}=0.01867mole$

$\Delta H=\frac{8.456kJ}{0.01867mole}=452.9kJ/mole$

Therefore, the molar heat of solution for the salt is 452.9 kJ/mole

4 0

3 years ago

A 4.5 kg box slides down a 4.3-m-high frictionless hill, starting from rest, across a 2.0-m-wide horizontal surface, then hits a

Rainbow [258]

Answer:

speed before reaching rough surface = 9.18 m/s

speed before hitting spring = 8.70 m/s

spring compression = 82 cm

number of complete trip = 9

Explanation:

Lets say

Position 1: On top of hill

Position 2: down the hill

Position 3: after the rough surface

Position 4: after hitting the spring

We'll strictly use conservation of energy for this equation

Potential energy on top of energy is full converted into kinetic energy down the hill (since surface is frictionless)

Hence, PEg1 = KE2

mgh = (1/2)mv2^2

(4.5)(9.8)(4.3) = (1/2)(4.5)v2^2

189.63 = (1/2)(4.5)v2^2

v2^2 = 2(9.8)(4.3) = 84.28

v2 = sqrt(84.28) = 9.18 m/s

After down the hill, it passes a rough surface. So some of the energy is loss due to friction forces

Friction force, Ff = u (coeff of kinetic friction ) x N (normal force)

Normal force, N = weight of box = mg = 4.5 x 9.8

Ff = 0.22 x 4.5 x 9.8

Work done / Energy loss = Wf = Ff x d (distance)

Wf = 0.22 x 4.5 x 9.8 x 2 = 19.404

Energy after passing the rough surface is totally kinetic energy

KE3 = KE2 - Wf = 189.63 - 19.404 = 170.226

speed after rough surface,

(1/2)mv3^2 = 170.226

v3 = sqrt((2 x 170.226)/4.5) = 8.70 m/s

After hitting the spring, all the kinetic energy is converted into potential energy of spring

170.226 = (1/2)kx^2

x^2 = 2 x 170.226 / 510 {note that constant of spring, k = 510}

x^2 = 0.668

x = sqrt(0.668) = 0.82m (82 cm)

To calculate complete trip before the box coming to rest, note that the only place where it loss energy is at the rough surface.

Energy before the first time pass rough surface = 189.63

Energy loss each time passing rough surface = 19.404

189.63 / 19.404 = 9.773 (9 complete with balance of 0.773)

That mean, the box will pass the rough surface 9 complete trip before coming to rest

8 0

3 years ago

A box moves to the right along a rough, wooden surface. In which direction does the box experience a frictional force?

emmasim [6.3K]

Answer:

To the left, in the opposite direction of the object's motion.

Explanation:

This is because friction always apposes motion, and will act to stop motion.

To stop the box, friction would have to act in the left direction.

5 0

3 years ago

An entomologist (bug scientist) wants to determine if temperature changes how many times a cricket chirps. What is the dependent

murzikaleks [220]

Answer:

Number of times a cricket chirps.

Explanation:

Let us use a graph to understand the function Here the entomologist wants to know the effect of temperature on the number of chirps of a cricket so, the chirps should vary with temperature. The opposite cannot be true i.e., the temperature is not dependent on the number of chirps rather the number of chirps are dependent on temperature.

So, the x axis will be represent the temperature and the y axis will represent the number of chirps.

Hence, the dependent variable will be number of times a cricket chirps i.e., the y axis.

8 0

3 years ago

When a surface is illuminated with electromagnetic radiation of wavelength 480 nm, the maximum kinetic energy of the emitted ele

algol [13]

Answer:

Max kinetic energy for 340 nm wavelength will be $2.238\times 10^{-19}j$