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3 years ago

Give the number of significant figures in this number: 7.8 x 10¹²

1 answer:

8 0

The number is written in scientific notation.

The significant figures are the numbers known precisely plus 1 digit that is uncertain.

When the numbers are expressed in scientific notation all the digits before 10^n are significant.

So, 7 and 8 are significant figures and the answer is that the number of significant figures is 2.

Answer: 2

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What is the total pressure in a container with 256 mm Hg of Oz, 198 mm Hg of He,

irina1246 [14]

Answer:

P(total pressure) = 504 mmHg = 504mm/760mm/atm = 0.663 atm

Explanation:

Apply Dalton's Law of Partial Pressures.

P(total) = ∑Partial Pressures = ∑(256mm + 198mm + 48mm) = 504 mmHg

P(total pressure) = 504 mmHg = 504mm/760mm/atm = 0.663 atm

7 0

2 years ago

Ammonium nitrate is an ingredient in cold packs used by sports trainers for injured athletes. Calculate the change in temperatur

Ronch [10]

Answer:

See explanation

Explanation:

First, we need to use the correct expression:

Q = m*Cp*ΔT (1)

Q = n*ΔH (2)

These are the 2 expressions to calculate heat or energy.

Now, we want to know the change of temperature of the nitrate in water after being added, so with the innitial data of nitrate, we can calculate heat using the second expression. First, we need to calculate moles with the molecular mass:

n = m/MM

n = 42/80.1 = 0.52 moles

With these moles, we can calculate heat with the ΔH of this reaction:

Q = 0.52 * 25.7 = 13.364 kJ or 13,364 J

However, this heat as is being absorbed, the value would be negative.

Now that we have heat, we can use expression (1) and plug these values to solve for ΔT, but before, we need to know the total mass of the solution (water + nitrate)

m = 250 + 42 = 292 g

now, solving for ΔT:

-13,364 = 292 * 4.18 * ΔT

ΔT = -13,363 / (292 * 4.18)

ΔT = -10.95 °C

3 0

3 years ago

Be sure to answer all parts. Part 1 out of 2 how many electrophilic centers are present in acetyl chloride (ch3cocl)?

natima [27]

<h3>Answer:</h3>

There is One electrophilic center in acetyl chloride.

<h3>Explanation:</h3>

Electrophile is defined as any specie which is electron deficient and is in need of electrons to complete its electron density or octet. The main two types of electrophiles are those species which either contain positive charge (i.e. NO₂⁺, Cl⁺, Br⁺ e.t.c) or partial positive charge like that contained by the sp² hybridized carbon of acetyl chloride shown below in attached picture.

In acetyl chloride the partial positive charge on sp² hybridized carbon is generated due to its direct bonding to highly electronegative elements *with partial negative charge) like oxygen and chlorine, which tend to pull the electron density from carbon atom making it electron deficient and a good electrophile for incoming nucleophile as a center of attack.

7 0

3 years ago

Which of the following statements is not true regarding acids? (3 points)

horsena [70]

Answer:

Lewis acid is a substance that donates a lone-pair of electrons.

Explanation:

What is said in the statement corresponds to a Lewis base, not an acid. For example, NH3 is a Lewis base, since it is capable of donating its pair of electrons. Trimethylborane (Me3B) is a Lewis acid, since it is capable of accepting a solitary pair.

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3 years ago

Read 2 more answers

When an electron moves from a lower energy level to a higher energy level, the atom:

Ede4ka [16]

Answer:

A. absorbs light

Explanation:

For an electron to move from a lower energy level to a higher energy level, energy needs to be added to the atom.

In most cases this required energy will be light: The electron of the atom will absorb the energy of the light and move to a higher energy level.

When said electron comes back to the lower energy level, the atom will conversely give off light.

5 0

2 years ago