What is the molarity of a 5 L solution that contains 7.5 moles of NaOH?

179.1 g of water is in a Styrofoam calorimeter of negligible heat capacity. The initial T of the water is 16.1oC. After 306.9 g

taurus [48]

Answer:

the specific heat of the unknown compound is $c_u=0.412J/g \cdot C$

Explanation:

Generally the change in temperature of water is evaluated as

$\Delta T = T_2 -T_1$

Substituting 16.1°C for $T_1$ and 27.4°C for $T_2$

$\Delta T = 27.4 - 16.1$

$=11.3^oC$

Generally the change in temperature of unknown compound is evaluated as

$\Delta T_u = T_3 -T_2$

Substituting 27.4°C for $T_2$ and 94.3°C for $T_3$

$\Delta T = 94.3 - 27.4$

$=66.9^oC$

Since there is an increase in temperature then heat is gained by water and this can be evaluated as

$H_w = mc_w \Delta T$

Substituting 179.1 g for m , 4.18 J/g.C for $c_w$ (specific heat of water)

$H_w = 4.18 * 179.1 * 11.3$

$= 8459.6J$

Since there is a decrease in temperature then heat is lost by unknown compound and this can be evaluated as

$H_u = m_uc_u \Delta T_u$

By conservation of energy law

Heat lost = Heat gained

Substituting 306.9 g for $m_u$ , 8459.6J for $H_u$

$8459.6 = 306.9 * c_u * 66.9$

Therefore $c_u = \frac{8459.6}{308.9 *66.9}$

$=0.412J/g \cdot C$

4 0

3 years ago

A microscope containing two or more lenses is an

kicyunya [14]

A compound lens microscope.

6 0

3 years ago

What steps are involved in the process that turns sediment back to rock? Select all that apply.

jeyben [28]

Answer:

compaction and cementation

I love science by the way

4 0

3 years ago

Read 2 more answers

Does data from mass spectrometry indicate that modern scientists have made modifications to Dalton''s model? Justify.

Gelneren [198K]

John Dalton was a scientist who proposed that all matter consists of atoms. At this stage, no one had yet discovered neutrons and the nucleus. As a result, Dalton's model consisted of a single atom i.e. the atom was the smallest object.
A mass spectrometer is an instrument that is able to see what is inside an atom. Scientists have been able to prove that the item is not the smallest object in the world. Atoms are made up of smaller objects called protons, neutrons and electrons.
We can, therefore, safely conclude that data from mass spectrometry has helped modern scientists to make modifications to Dalton's model.

5 0

3 years ago

Will give lots of points if answered correctly. Determine the kb for chloroform when 0.793 moles of solute in 0.758 kg changes t

Liono4ka [1.6K]

Answer: The value of $K_{b}$ for chloroform is $3.62^{o}C/m$ when 0.793 moles of solute in 0.758 kg changes the boiling point by 3.80 °C.

Explanation:

Given: Moles of solute = 0.793 mol

Mass of solvent = 0.758

$\Delta T_{b} = 3.80^{o}C$

As molality is the number of moles of solute present in kg of solvent. Hence, molality of given solution is calculated as follows.

$Molality = \frac{no. of moles}{mass of solvent (in kg)}\\= \frac{0.793 mol}{0.758 kg}\\= 1.05 m$

Now, the values of $K_b$ is calculated as follows.

$\Delta T_{b} = i\times K_{b} \times m$

where,

i = Van't Hoff factor = 1 (for chloroform)

m = molality

$K_{b}$ = molal boiling point elevation constant

Substitute the values into above formula as follows.

$\Delta T_{b} = i\times K_{b} \times m\\3.80^{o}C = 1 \times K_{b} \times 1.05 m\\K_{b} = 3.62^{o}C/m$

Thus, we can conclude that the value of $K_{b}$ for chloroform is $3.62^{o}C/m$ when 0.793 moles of solute in 0.758 kg changes the boiling point by 3.80 °C.

7 0

3 years ago