All categories

3 years ago

What do the superscripts in an electron configuration represent?

Chemistry

1 answer:

zmey [24]3 years ago

8 0

Answer: number of electron in respective sub shell or orbital

Explanation:

You might be interested in

Who wrote the first modern chemical textbook?

grin007 [14]

<span>Antoine Lavoisier is the answer </span>

5 0

3 years ago

Read 2 more answers

Some plant seeds are adapted to develop only at extremely high temperatures. For what environmental change are

Hoochie [10]

Answer:

Forest Fire

Explanation:

Forest fire is an ecological factor over which biological processes like seed dispersal and their germination is dependent upon. Some plants germinate under high temperature underground regions of the soil which is covered by the hot soil affected by the burning by the forest fire. Some of the coniferous trees like longpole pines have hard cone which exhibit the seeds. These cones exhibit the serotonin resins which are melted by the forests fire hence fire helps in dispersal of the seeds. Other plants like Eucalyptus and Banksia are also dependent upon fire for seed dispersal.

4 0

3 years ago

Read 2 more answers

Calculate Delta H in KJ for the following reactions using heats of formation:

lozanna [386]

Answer:

$\Delta H\textdegree = -2856.8\;\text{kJ}$ per mole reaction.

$\Delta H\textdegree = -22.3\;\text{kJ}$ per mole reaction.

Explanation:

What is the standard enthalpy of formation $\Delta H_f\textdegree{}$ of a substance? $\Delta H_f\textdegree{}$ the enthalpy change when one mole of the substance is formed from the most stable allotrope of its elements under standard conditions.

Naturally, $\Delta H_f\textdegree{} = 0$ for the most stable allotrope of each element under standard conditions. For example, oxygen $\text{O}_2$ (not ozone $\text{O}_3$ ) is the most stable allotrope of oxygen. Also, under STP $\text{O}_2$ is a gas. Forming $\text{O}_2\;(g)$ from itself does not involve any chemical or physical change. As a result, $\Delta H_f\textdegree{} = 0$ for $\text{O}_2\;(g)$ .

Look up standard enthalpy of formation $\Delta H_f\textdegree{}$ data for the rest of the species. In case one or more values are not available from your school, here are the published ones. Note the state symbols of the compounds (water/steam $\text{H}_2\text{O}$ in particular) and the sign of the enthalpy changes.

$\text{C}_2\text{H}_6\;(g)$ : $-84.0\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\text{CO}_2\;(g)$ : $-393.5\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\text{H}_2\text{O}\;{\bf (g)}$ : $-241.8\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\text{PbO}\;(s)$ : $-217.9\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\text{PbO}_2\;(s)$ : $-276.6\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\text{Pb}_3\text{O}_4\;(s)$ : $-734.7\;\text{kJ}\cdot\text{mol}^{-1}$

How to calculate the enthalpy change of a reaction $\Delta H_\text{rxn}$ (or simply $\Delta H$ from enthalpies of formation?

Multiply the enthalpy of formation of each product by its coefficient in the equation.
Find the sum of these values. Label the sum $\Sigma (n\cdot \Delta_f(\text{Reactants}))$ to show that this value takes the coefficients into account.
Multiply the enthalpy of formation of each reactant by its coefficient in the equation.
Find the sum of these values. Label the sum $\Sigma (n\cdot \Delta_f(\text{Products}))$ to show that this value takes the coefficient into account.
Change = Final - Initial. So is the case with enthalpy changes. $\Delta H_\text{rxn} = \Sigma (n\cdot \Delta_f(\textbf{Products})) - \Sigma (n\cdot \Delta_f(\textbf{Reactants}))$ .

For the first reaction:

$\Sigma (n\cdot \Delta_f(\text{Reactants})) = 4\times (-393.5) + 6\times (-241.8) = -3024.8\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\Sigma (n\cdot \Delta_f(\text{Products})) = 2\times (-84.0) + 7\times 0 = -168.0\;\text{kJ}\cdot\text{mol}^{-1}$ ;
$\begin{aligned}\Delta H_\text{rxn} &= \Sigma (n\cdot \Delta_f(\textbf{Products})) - \Sigma (n\cdot \Delta_f(\textbf{Reactants}))\\ &= (-3024.8\;\text{kJ}\cdot\text{mol}^{-1}) - (-168.0\;\text{kJ}\cdot\text{mol}^{-1})\\ &= -2856.8\;\text{kJ}\cdot\text{mol}^{-1} \end{aligned}$ .

Try these steps for the second reaction:

$\Delta H_\text{rxn} = -22.3\;\text{kJ}\cdot\text{mol}^{-1}$ .

6 0

4 years ago

The Karez well system _______. a. was the first known use of wells b. was a postindustrial system c. transported groundwater fro

Lelu [443]

The Karez Well System is an important ancient irrigation system. It is made up of a horizontal series of vertical dug wells that are linked to each other by underground water canals. This system provides water to drink for local people as well as to water their crops. The water was collected from the mountains which are miles away from the farmland. Thus, this system transfers water from mountains in form of groundwater to people which are miles away.

Hence, the Karez well system transported groundwater from a distance.

6 0

4 years ago

Read 2 more answers

What is the pH of a solution that has a [H+] of 1.5 × 10−5 M?

Alexandra [31]

pH = 4.82

[H⁺] = 1.5 × 10⁻⁵ mol·L⁻¹.

pH = -log[H⁺] = -log(1.5 × 10⁻⁵) = 4.82

8 0

3 years ago