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2 years ago

During what change is heat absorbed?

Chemistry

2 answers:

Alisiya [41]2 years ago

6 0

Endothermic reactions absorb heat and exotbermic releases heat

Ostrovityanka [42]2 years ago

3 0

Answer: endothermic

Explanation: A chemical reaction or physical change is endothermic if heat is absorbed by the system from the surroundings.

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The four elements that make up about 96% of body matter are ________.

AveGali [126]

An element is a pure substance that cannot be separated or divided into simpler substances by any method (physical or chemical). The four common elements in all the living organisms are carbon, oxygen, hydrogen, nitrogen.

Thus, the four elements that make up about 96 % of body matter are carbon, oxygen, hydrogen, nitrogen (c).

4 0

3 years ago

Read 2 more answers

How many grams of Fe2+ are there in 0.003109 moles of Fe2+?

Sergio [31]

Answer: 0.174 g

Explanation:

First of all understand that charge on an atom like here 2+ will not vary molar mass. because ions are formed by loss or gain of electrons and electrons do not contribute to the mass of an atom or ion. so losing or gaining electron doesnt create any difference.

molar mass of Fe, i.e. mass of 1 mole of Fe is 56 g. So, mass of 1 mole of Fe2+ will also be 56 g.

given is 0.003109 moles of Fe2+,

Use maths,

1 mole of Fe2+ weighs 56 g

So, 0.003109 moles will weigh = (56 g / 1 mol ) x 0.003109 = 0.174 g.

7 0

3 years ago

Why do electrons transition between energy levels within the atom, and how do we detect these transitions?

Sedaia [141]

Answer:

See explanation

Explanation:

Electrons transition between energy levels in an atom due to gain or loss of energy. An electron may gain energy and move from its ground state to one of the accessible excited states. The electron quickly returns to ground state, emitting the energy previously absorbed as a photon of light. The wavelength of light emitted is measured using powerful spectrometers.

Atoms can be excited thermally or by irradiation with light of appropriate frequency.

7 0

3 years ago

Use the balanced equation from number four above to determine the limiting reactant if we had a mixture of 5.0 moles of Fe and 4

Tom [10]

Answer:

2Fe + 3O₂ → 2Fe₂O₃

Limiting reactant: O₂

2Fe + O₂ → 2FeO

Limiting reactant: Fe

Explanation:

2Fe + 3O₂ → 2Fe₂O₃

2Fe + O₂ → 2FeO

These are the possible reactions:

In first case, 2 moles of Fe need 3 mol of oyxgen to react

If I have 5 moles of Fe, I will need (5 .3)/2 = 7.5 moles of O₂

Then, the oxygen is my limiting ( I only have 4 moles)

3 moles of O₂ need 2 moles of Fe

If I have 4 moles of O₂, I will need (4 .2)/3 = 2.66 moles (I have 5)

Fe, is the reactant in excess.

For second case, 2 moles of Fe need 1 mol of O₂, to react.

If I have 5 moles of Fe, I will need ( 5 .1) / 2 =2.5 moles of O₂

I have 4 moles of oxygen, so now it is my excess.

1 mol of O₂ need 2 moles of Fe, to react

If I have 4 moles of O₂, I will need the double of amount, 8 moles of Fe.

I have 5 moles, then the Fe is my limtiing reactant.

8 0

3 years ago

Definition of phosphoric acid

miss Akunina [59]

Phosphoric acid is an acid used in fertilizers and soaps.

 Hope this helps:)

8 0

3 years ago