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4 years ago

Which pair are classified as chemical substances? Pick two.

1 answer:

8 0

Elements and compounds. This is because in solutions and mixtures the substances are not bonded to each other or pure, you can separate and purify substances in solutions and mixtures (via techniques such as distillation, filtering) but you cannot separate compounds as they are bonded together.

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How does the energy of an electron change when the electron moves closer to the nucleus?

tankabanditka [31]

It increases. B.

Close to the nucleus are high energy levels, because of the pull of the nucleus. But farther away from the nucleus, the electrons there are of low energy level.

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4 years ago

What kind of material makes ice cream

aivan3 [116]

Is it milk and nitrogen? Hope this helps!

7 0

3 years ago

Read 2 more answers

If this decay has a half life of 2.60 years, what mass of 72.5 g of sodium 22 will remain after 15.6 years

Vlad1618 [11]

Sodium-22 remain : 1.13 g

<h3>Further explanation </h3>

The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.

Usually, radioactive elements have an unstable atomic nucleus.

General formulas used in decay:

$\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{T/t\frac{1}{2} }}}$

T = duration of decay

t 1/2 = half-life

N₀ = the number of initial radioactive atoms

Nt = the number of radioactive atoms left after decaying during T time

half-life = t 1/2=2.6 years

T=15.6 years

No=72.5 g

$\tt Nt=72.5.\dfrac{1}{2}^{15.6/2.6}\\\\Nt=72.5.\dfrac{1}{2}^6\\\\Nt=1.13~g$

8 0

4 years ago

Why ddo all collisions between reactant molecules not lead to reaction.

jok3333 [9.3K]

Answer:

The colliding molecules need to possess certain energy which is greater than the activation energy Ea and proper orientation.

<h3>Not all collisions result in a chemical reaction because not all collisions have the have sufficient amount of energy or have the appropriate activation energy. Nor do they all have this correct orientation. Molecules need to collide in such a way that they're oriented, so the correct bonds could break in. The correct bonds conform. And then, of course, they need to have sufficient activation energy in order to initiate the breaking of the bonds.</h3>

<h3>Hope this helps please let me know If I'm wrong.</h3>

7 0

2 years ago

Estimate ΔH for the reaction: C2H6(g) + Cl2(g)--> C2H5Cl(g) + HCl(g) given the following average bond energies (in kJ/mol): C

Leno4ka [110]

Explanation:

The reaction equation will be as follows.

$C_{2}H_{6}(g) + Cl_{2}(g) \rightarrow C_{2}H_{5}Cl(g) + HCl(g)$

Using bond energies, expression for calculating the value of $\Delta H$ is as follows.

$\Delta H = \sum B.E_{reactants} - \sum B.E_{products}$

On reactant side, from $C_{2}H_{6}$ number of bonds are as follows.

C-C bonds = 1

C-H bonds = 6

From $Cl_{2}$ ; Cl-Cl bonds = 1

On product side, from $C_{2}H_{5}Cl$ number of bonds are as follows.

C-C bonds = 1

C-H bonds = 5

C-Cl bonds = 1

From HCl; H-Cl bonds = 1

Hence, using the bond energies we will calculate the enthalpy of reaction as follows.

$\Delta H = \sum B.E_{reactants} - \sum B.E_{products}$

= $[(1 \times 348 kJ/mol) + (6 \times 414 kJ/mol) + (1 \times 242 kJ/mol)] - [(1 \times 348 kJ/mol) + (5 \times 414 kJ/mol) + (1 \times 327 kJ/mol) + (1 \times 431 kJ/mol)]$ = -102 kJ/mol

Thus, we can conclude that change in enthalpy for the given reaction is -102 kJ/mol.

5 0

3 years ago