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3 years ago

In which direction does heat energy move?

2 answers:

defon3 years ago

8 0

C

Heat usually flows to colder objects in order to make them both the same temperature and when the colder object finally gets hot and is the same temperature as the hotter object it stops flowing hope this helps:)

liq [111]3 years ago

4 0

Answer:

Explanation:

Because when a cold object is cold it start to get warm because Of the air.

and it start to warm and it gets warm.

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Consider the following intermediate chemical equations.

QveST [7]

Answer: 250 kJ

Explanation: According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to Hess’s law, the chemical equation can be treated as algebraic expressions and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

$P_4(s)+6Cl_2\rightarrow 4PCl_3$ $\Delta H_1=-2439kJ$ (1)

$4PCl_5(g)\rightarrow P_4(s)+10Cl_2(g)$ $\Delta H_2=3438kJ$ (2)

Net chemical equation:

$PCl_5(g)\rightarrow PCl_3(g)+Cl_2(g)$ $\Delta H=?$ (3)

Adding 1 and 2 we get,

$4PCl_5(g)\rightarrow 4PCl_3(g)+4Cl_2$ $\Delta H_3=\Delta H_1+\Delta H_2=-2439+3438=1000kJ$ (4)

Now dividing equation (4) by 4, we get

$PCl_5(g)\rightarrow PCl_3(g)+Cl_2$

$\Delta H=\frac{\Delta H_3}{4}=\frac{1000kJ}{4}=250kJ$ (4)

8 0

3 years ago

Calculate the pH of the solutions: [H^+]= 1.6 x 10^-3 M

Yuliya22 [10]

Answer:

A) pH = 2.8

B) pH = 5.5

C) pH = 8.9

D) pH = 13.72

Explanation:

a) [H⁺] = 1.6 × 10⁻³ M

pH = -log [H⁺]

pH = -log [1.6 × 10⁻³ ]

pH = 2.8

b) [H⁺] = 3 × 10⁻⁶

pH = -log [H⁺]

pH = -log [3 × 10⁻⁶ ]

pH = 5.5

c) [OH⁻] = 8.2 × 10⁻⁶

pOH = -log[OH]

pOH = -log[8.2 × 10⁻⁶]

pOH = 5.1

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 5.1

pH = 8.9

d) [OH⁻] = 0.53 M

pOH = -log[OH]

pOH = -log[0.53]

pOH = 0.28

pH + pOH = 14

pH = 14 - pOH

pH = 14 - 0.28

pH = 13.72

5 0

3 years ago

A certain radioactive isotope decays at a rate of 0.2% annually. Determine the half-life of this isotope, to the nearest year

pychu [463]

Answer:

The half-life of the radioactive isotope is 346 years.

Explanation:

The decay rate of the isotope is modelled after the following first-order linear ordinary differential equation:

$\frac{dm}{dt} = -\frac{m}{\tau}$

Where:

$m$ - Current isotope mass, measured in kilograms.

$t$ - Time, measured in years.

$\tau$ - Time constant, measured in years.

The solution of this differential equation is:

$m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }$

Where $m_{o}$ is the initial mass of the isotope. It is known that radioactive isotope decays at a yearly rate of 0.2 % annually, then, the following relationship is obtained: