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3 years ago

1.5 What is the purpose of adding sodium carbonate to the reaction mixture? I

1 answer:

7 0

Answer: As sodium carbonate is added, bubbles of carbon dioxide form. When all the acid has been neutralised, adding sodium carbonate will no longer produce bubbles of carbon dioxide gas. The final rinsing with water should remove traces of the water soluble salt formed.

Explanation:

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A 100 gram glass container contains 200 grams of water and 50.0 grams of ice all at 0°c. a 200 gram piece of lead at 100°c is ad

ASHA 777 [7]

$0 \; \textdegree{\text{C}}$

Explanation:

Assuming that the final (equilibrium) temperature of the system is above the melting point of ice, such that all ice in the container melts in this process thus

$E(\text{fusion}) = m(\text{ice}) \cdot L_{f}(\text{water}) = 66.74 \; \text{kJ}$ and
$m(\text{water, final}) = m(\text{water, initial}) + m(\text{ice, initial}) = 0.250 \; \text{kg}$

Let the final temperature of the system be $t \; \textdegree{\text{C}}$ . Thus $\Delta T (\text{water}) = \Delta T (\text{beaker}) = t(\text{initial}) - t_{0} = t \; \textdegree{\text{C}}$

$Q(\text{water}) &= &c(\text{water}) \cdot m(\text{water, final}) \cdot \Delta T (\text{water})= 1.047 \cdot t\; \text{kJ}$ (converted to kilojoules)
$Q(\text{container}) &= &c(\text{glass}) \cdot m(\text{container}) \cdot \Delta T (\text{container})= 0.0837 \cdot t \; \text{kJ}$
$Q(\text{lead}) &= &c(\text{lead}) \cdot m(\text{lead}) \cdot \Delta T (\text{lead})= 0.0255 \cdot (100 - t)\; \text{kJ}$

The fact that energy within this system (assuming proper insulation) conserves allows for the construction of an equation about variable $t$ .

$E(\text{absorbed} ) = E(\text{released})$

$E(\text{absorbed} ) = E(\text{fushion}) + Q(\text{water}) + Q(\text{container})$
$E(\text{released}) = Q(\text{lead})$

Confirm the uniformity of units, equate the two expressions and solve for $t$ :

$66.74 + 1.047 \cdot t + 0.0837 \cdot t = 0.0255 \cdot (80 - t)$

$t \approx -55.95\; \textdegree{\text{C}} < 0\; \textdegree{\text{C}}$ which goes against the initial assumption. Implying that the final temperature does <em>not</em> go above the melting point of water- i.e., $t \le 0 \; \textdegree{\text{C}}$ . However, there's no way for the temperature of the system to go below $0 \; \textdegree{\text{C}}$ ; doing so would require the removal of heat from the system which isn't possible under the given circumstance; the ice-water mixture experiences an addition of heat as the hot block of lead was added to the system.

The temperature of the system therefore remains at $0 \; \textdegree{\text{C}}$ ; the only macroscopic change in this process is expected to be observed as a slight variation in the ratio between the mass of liquid water and that of the ice in this system.

3 0

3 years ago

Balance the following reaction:

miv72 [106K]

The balanced reaction is as below

3A₂B + 2DC₃→ 6 AC + D₂B₃

The number that must be to the left of AC is 6

Explanation

According to the law of mass conservation , the number of atoms in reactant side must be equal to number to the number of atoms in product side.

Therefore the equation above is balance since it obey the law of mass conservation.

For example there is 6 atoms of A in reactant side and 6 in product side.

5 0

3 years ago

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On a cool morning, uyen’s breath can form a cloud when she breathes out. which changes of state are most responsible for uyen se

Ganezh [65]

<span>You may already know that when you breathe in, your body takes in oxygen from the air. When you breathe out, your lungs expel carbon dioxide back into the air. But the breath you breathe out contains more than just carbon dioxide.</span>

When you exhale (breathe out), your breath also containsmoisture. Because your mouth and lungs are moist, each breath you exhale contains a little bit of water in the form of water vapor(the gas form of water).

For water to stay a gas in the form of water vapor, it needs enough energy to keep its molecules moving. Inside your lungs where it's nice and warm, this isn't a problem.

4 0

3 years ago

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The meselson-stahl experiment demonstrated that DNA replication is semi conservative in the figure semi conservative replication

Vlad1618 [11]

Answer:

The correct answer will be option-D.

Explanation:

The semi-conservative mode of replication is the common method of replication used by mostly organisms on earth which were demonstrated by the Meselson and Stahl in 1958.

They used the isotopes of the nitrogen which contains extra neuron which makes the nitrogen-heavy and cultured them in bacteria

The experiment concluded that newly replicated double stranded DNA contains one newly synthesized DNA strand which is complementary to another parental strand. Thus new DNA molecule has one parental strand while other newly synthesized strand.

This is best illustrated by the option-D in the figure and therefore is the correct answer.

7 0

3 years ago

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What is a way in which nuclear fusion is used?

Marta_Voda [28]

Answer:It is a nuclear process, where energy is produced by smashing together light atoms. It is the opposite reaction of fission, where heavy isotopes are split apart.

Explanation Fusion is the process by which the sun and other stars generate light and heat.

It’s most easily achieved on Earth by combining two isotopes of hydrogen: deuterium and tritium. Hydrogen is the lightest of all the elements, being made up of a single proton and a electron. Deuterium has an extra neutron in its nucleus; it can replace one of the hydrogen atoms in H20 to make what is called “heavy water.”

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3 years ago