5. The mass of cobalt-60 in a sample is found to have decreased from 0.800g to 0.200g in a

An aqueous solution contains 0.100 m naoh at 25.0 °c. the ph of the solution is ________.

ikadub [295]

Recall; pH + pOH = 14
In this case [OH-] =0.100 m
therefore;
pOH = -LOG[OH-]
= - Log (0.100)
= 1.00
Therefore; the pOH is 1.00
And since, pH +pOH = 14
Then pH = 14-pOH
= 14 -1
= 13
Thus the pH is 13.00

7 0

3 years ago

What is the density of a substance that weighs 340g and has a volume of 40cm3?

jeka94

Answer:

Explanation:

The density of a substance can be found by using the formula

$density = \frac{mass}{volume} \\$

From the question we have

$density = \frac{340}{40} = \frac{17}{2} \\$

We have the final answer as

Hope this helps you

5 0

3 years ago

Materials expand when heated. Consider a metal rod of length L0 at temperature T0. If the temperature is changed by an amount ΔT

marysya [2.9K]

Answer:

(a) The length at temperature 180°C is 40.070 cm

(b) The length at temperature 90°C is 64.976 inches

(c) L(T, α) = 60·α·T - 9000·α + 60

Explanation:

(a) The given parameters are

The thermal expansion coefficient, α for steel = 1.24 × 10⁻⁵/°C

The initial length of the steel L₀ = 40 cm

The initial temperature, t₀ = 40°C

The length at temperature 180°C = L

Therefore, from the given relation, for change in length, ΔL, we have;

ΔL = α × L₀ × ΔT

The amount the temperature changed ΔT = 180°C - 40°C = 140°C

Therefore, the change in length, ΔL, is found as follows;

ΔL = α × L₀ × ΔT = 1.24 × 10⁻⁵/°C × 40 × 140°C = 0.07 cm

Therefore, L = L₀ + ΔL = 40 + 0.07 = 40.07 cm

The length at temperature 180°C = 40.07 cm

(b) Given that the length at T = 120°C is 65 in., we have;

The temperature at which the new length is sought = 90°C

The amount the temperature changed ΔT = 90°C - 120°C = -30°C

ΔL = α × L₀ × ΔT = 1.24 × 10⁻⁵/°C × 65 × -30°C = -0.024375 inches

The length, L at 90°C is therefore, L = L₀ + ΔL = 65 - 0.024375 = 64.976 in.

The length at temperature 90°C = 64.976 inches

(c) L = L₀ + ΔL = L₀ + α × L₀ × ΔT = L₀ + α × L₀ × (T - T₀)

Therefore;

L = 60 + α × 60 × (T - 150°C)

L = 60 + α × 60 × T - 9000 × α

L(T, α) = 60·α·T - 9000·α + 60

7 0

3 years ago

Consider a possible triatomic molecule containing a nitrogen, oxygen, and fluorine atoms for the following questions.

STALIN [3.7K]

Answer:

a) nitrogen

b) nitrogen =5

Oxygen = 6

Fluorine =7

Explanation:

Usually, if we have two or more elements in a compound, the central atom in the compound is the atom having the least value of electro negativity.

If we consider fluorine, oxygen and nitrogen; nitrogen is the least electronegative of the trio hence it should be the central atom of the triatomic molecule.

The number of valence electrons on the valence shell of each atom is shown below;

nitrogen =5

Oxygen = 6

Fluorine =7

5 0

3 years ago

To interconvert the concentration units molality (m) and mass percent, you must also know the density of the solution. A) True B

uranmaximum [27]

Answer:

The correct answer is option false.

Explanation:

Molality of the solution defined as moles of substance present in 1 kilogram of solvent.

Moles = $\frac{Mass of solute}}{\text{molar mass of solute}}$

$Molality=\frac{Moles}{\text{Mass of solvent(kg)}}$

Mass of percent (w/w%) of the solution is defined as amount of solute present in 100 grams of solution.

$(w/w\%)_=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$

So, if want to inter-convert molality into mass percent we can do that without knowing density of solution.

Mass of solution = Mass of solute + Mass of solvent

7 0

3 years ago