Who recognized that elements properties repeated at regular intervals

The enthalpy change for converting 1.00 mol of ice at -50.0 ∘c to water at 60.0∘c is ________ kj. the specific heats of ice, wat

guajiro [1.7K]

First, we have to get:

1- The heat required to increase T of ice from -50 to 0 °C:

according to q formula:

q1 = m*C*ΔT

when m is the mass of ice = mol * molar mass

= 1 mol * 18 mol/g

= 18 g

and C is the specific heat capacity of ice = 2.09 J/g-K

and ΔT change in temperature = 0- (-50) = 50°C

by substitution:

∴q1 = 18 g * 2.09 J/g-K *50°C

= 1881 J = 1.881 KJ

2- the heat required to melt this mass of ice is :

q2 = n*ΔHfus

when n is the number of moles of ice = 1 mol

and ΔHfus = 6.01 KJ/mol

by substitution:

q2 = 1 mol * 6.01 KJ/mol

= 6.01 KJ

3- the heat required to increase the water temperature from 0°C to 60 °C is:

q3 = m*C*ΔT

when m is the mass of water = 18 g

C is the specific heat capacity of water = 4.18 J/g-K

ΔT is the change of Temperature of water = 60°C - 0°C = 60°C

by substitution:

∴q3 = 18 g * 4.18 J/g-K * 60°C

= 4514 J = 4.514 KJ

∴the total change of enthalpy = q1+q2+q3

= 1.881 KJ +6.01 KJ + 4.514 KJ

= 12.405 KJ

5 0

3 years ago

1. A sample of oxygen is collected over water at 22 ° C and 762 torr. What is the partial pressure of the dry oxygen? The vapor

Rom4ik [11]

Answer: The partial pressure of the dry oxygen is 742 torr

Explanation:

Dalton's Law of Partial Pressure states that the total pressure exerted by a mixture of gases is the sum of partial pressure of each individual gas present. Thus $P(total)=P_1+P_2 .........$

Given; Total pressure = 762 torr

partial pressure of water = 19.8 torr

partial pressure of dry oxygen = ? torr

Total pressure = partial pressure of water + partial pressure of dry oxygen

762 torr = 19.8 torr = partial pressure of dry oxygen

partial pressure of dry oxygen = 742 torr

The partial pressure of the dry oxygen is 742 torr

8 0

3 years ago

The standard free energy of activation of one reaction A is 95.00 kJ mol–1 (22.71 kcal mol–1). The standard free energy of activ

diamong [38]

Answer:

The answer to the questions are as follows

Reaction B is 4426.28 times faster than reaction A

(b) Reaction B is faster.

Explanation:

To solve the question we are meant to compare both reactions to see which one is faster

The values of the given activation energies are as follows

For A

Ea = 95.00 kJ mol–1 (22.71 kcal mol–1) and

for B

Ea = 74.20 kJ mol–1 (17.73 kcal mol–1)

T is the same for both reactions and is equal to 298 k

Concentration of both reaction = 1M

The Arrhenius Law is given by

k = $Ae^{\frac{-E_{a} }{RT} }$

Where

k = rate constant

Ea = activation energy

R = universal gas constant

T = temperature (Kelvin )

A = Arrhenius factor

Therefore

For reaction A, the rate constant k₁ is given by k₁ = $Ae^{\frac{-95000}{(8.314)(298)} }$

And for B the rate constant k₂ is given by k₂ = $Ae^{\frac{-74200 }{(8.314)(298)} }$

k₁ = A×2.225×10⁻¹⁷

k₂ = A×9.850×10⁻¹⁴

As seen from the above Reaction B is faster than reaction A by (A×9.850×10⁻¹⁴)/(A×2.225×10⁻¹⁷) or 4426.28 times

3 0

3 years ago

Explain why world food shortages could be reduced by growing more algae.

Sonja [21]

One of the many awe-inspiring things about algae, Professor Greene explains, is that they can grow between ten and 100 times faster than land plants. In view of this speedy growth rate – combined with the fact they can thrive virtually anywhere in the right conditions – growing marine microalgae could provide a variety of solutions to some of the world’s most pressing problems.

Take, global warming. Algae sequesters CO2, as we have learned, but owing to the fact they grow faster than land plants, can cover wider areas and can be utilised in bioreactors, they can actually absorb CO2 more effectively than land plants. AI company Hypergiant Industries, for instance, say their algae bioreactor was 400 times more efficient at taking in CO2 than trees.

And it’s not just their nutritional credentials which could solve humanity’s looming food crisis, but how they are produced. Marine microalgae grow in seawater, which means they do not rely on arable land or freshwater, both of which are in limited supply. Professor Greene believes the use of these organisms could therefore release almost three million km2 of cropland for reforestation, and also conserve one fifth of global freshwater

8 0

2 years ago

Which statements are true?

schepotkina [342]

Explanation:

Evaporation is defined as a process in which liquid state of water is changing into vapor state.

So, we need to break the bonds of liquid substance in order to convert it into vapor state. And, energy is absorbed for breaking of bonds which means that evaporation is an endothermic process.

Hence, the statement evaporation of water is an exothermic process is false.

When a hydrocarbon reacts with oxygen and leads to the formation of carbon dioxide and water then this type of reaction is known as combustion reaction.

A combustion reaction will always release heat energy. Hence, combustion reaction is exothermic in nature.

When energy is transferred as heat from the surroundings to the system then it means energy is being absorbed by the system. And, absorption of heat is an endothermic process for which $\Delta H$ is positive.

Whereas when energy is transferred from system to the surrounding then it means energy is released by the system which is an exothermic process.

Hence, for an exothermic process value of $\Delta H$ is negative.

Thus, we can conclude that statements which are true are as follows.

A combustion reaction is exothermic.

When energy is transferred as heat from the system to the surroundings, $\Delta H$ is negative.

For an endothermic reaction Deta H is positive.

5 0

2 years ago