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Vladimir [108]
3 years ago
9

Which of these elements has four valence electrons

Chemistry
1 answer:
exis [7]3 years ago
7 0
What are the elements?

You might be interested in
Calculate the change in energy when 75.0 grams of water drops from<br> 31.0C to 21.6.
zysi [14]

Answer: Step 1: Calculate qsur (the surrounding is

usually the water)

qsur = ? J

m = 75.0 g water

c = 4.184 J/g

oC

ΔT = (Tfinal- Tinitial)= (21.6 – 31.0) = -9.4 oC

qsur = m · c · (ΔT)

qsur = (75.0g) (4.184 J/g

oC) (-9.4 oC)

qsur = - 2949.72 J

First, using the information we know that we

must solve for qsur, which is the water. We know

the mass for water, 75.0g, the specific heat of

the water, 4.184 j/g

o

c, and the change in

temperature, 21.6-31.0 = -9.4 oC. Plugging it

into the equation, we solve for qsur.

Step 2: Calculate qsys qsys = - (qsur)

qsys = - (- 2949.72 J)

qsys = + 2949.72

In this case, the qsur is negative, which means

that the water lost energy. Where did it go? It

went to the system. Thus, the energy of the

system is negative, opposite, the energy of the

surrounding.

Step 3: Calculate moles of the substance

that is the system

Given: 12.8 g KCl

Mol system = (g system given)

(molar mass of system)

Mol system = (12.8 g KCl)

(39.10g + 35.45g)

Mol system = 12.8 g KCl

74.55 g

Mol system = 0.172

Here, we solve for the mol in the system by

using the molar mass of the material in the

system.

Step 4: Calculate ΔH ΔH = q sys .

Mol system

ΔH= + 2949.72 J

0.172 mol

ΔH= +17179.81 J/mol or +1.72 x 104

J/mol

i hope this helps

5 0
3 years ago
Read 2 more answers
Which statement is correct for the element of proton number 19?
BlackZzzverrR [31]

Answer:

D

Explanation:

From periodic table : proton number 19  corresponds to K  (potassium)

  which is very reactive with water

8 0
2 years ago
What is the rate of change in velocity
luda_lava [24]
The rate of change in velocity<span> is called acceleration.</span>
3 0
3 years ago
When a piece of sodium carbonate reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then the s
siniylev [52]
Gas x would be carbon dioxide.

note/ acid + carbonate —> salt + water + carbon dioxide

the white precipitate would be calcium carbonate. CaCo₃

note/ this is a common eqn u need to remember.

X - CO₂ (carbón dioxide)
Y - CaCo₃ (calcium carbonate)

sodium carbonate is a basic salt
7 0
3 years ago
3. Are quartz and coal minerals or only naturally occurring<br> substances?
klasskru [66]

Answer:

minerals

Explanation:

coal is made from decomposing matter

6 0
3 years ago
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