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2 years ago

Which statement concerning elements is true?(1) Different elements must have different numbers of isotopes.

1 answer:

4 0

The correct statement is <span>(4) All atoms of a given element must have the same atomic number.

Atoms come in different isotopes(which have different mass), which differ in the number of neutrons, but are still the same element (this tells you why the other options are bad).
</span>

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And with solution...

Tems11 [23]

Answer:

The answer to your question is: V = 6.93 L

Explanation:

Data

N₂ = 5.6 g

Volume of NH₃ = ?

14 g of N ---------------- 1 mol

5.6 g ----------------------- x

x = (5.6 x 1) / 14 = 0.4 mol of N

Reaction

N₂ + 3H₂ ⇒ 2NH₃

1 mol of N₂ ---------------- 2 moles of NH₃

0.4 mol of N₂ -------------- x

x = (0.4 x 2) / 1

x = 0.8 mol of NH₃

Formula

PV = nRT

P = 5200 torr = 6.84 atm

V = ?

n = 0.8

R = 0.082 atm L/ mol °K

T = 450°C = 723°K

Substitution

V = (0.8)(0.082)(723) / 6.84

V = 6.93 L

7 0

2 years ago

What are the pH of these solutions?

Tju [1.3M]

Answer:

The answer to your question is below

Explanation:

a) HCl 0.01 M

pH = -log [0.01]

pH = - (-2)

pH = 2

b) HCl = 0.001 M

pH = -log[0.001]

pH = -(-3)

pH = 3

c) HCl = 0.00001 M

pH = -log[0.00001]

pH = - (-5)

pH = 5

d) Distilled water

pH = 7.0

e) NaOH = 0.00001 M

pOH = -log [0.00001]

pOH = -(-5)

pH = 14 - 5

pH = 9

f) NaOH = 0.001 M

pOH =- log [0.001]

pOH = 3

pH = 14 - 3

pH = 11

g) NaOH = 0.1 M

pOH = -log[0.1]

pOH = 1

pH = 14 - 1

pH = 13

3 0

2 years ago

Starting with 2.50 mol of N2 gas (assumed to be ideal) in a cylinder at 1.00 atm and 20.0C, a chemist first heats the gas at con

arsen [322]

Answer:

a) $T_b=590.775k$

b) $W_t=1.08*10^4J$

d) $Q=3.778*10^4J$

d) $\triangle V=4.058*10^4J$

Explanation:

From the question we are told that:

Moles of N2 $n=2.50$

Atmospheric pressure $P=100atm$

Temperature $t=20 \textdegree C$

$t = 20+273$

$t = 293k$

Initial heat $Q=1.36 * 10^4 J$

Generally the equation for change in temperature is mathematically given by

$\triangle T=\frac{Q}{N*C_v}$

Where

$C_v=Heat\ Capacity \approx 20.76 J/mol/K$

$T_b-T_a=\frac{1.36 * 10^4 J}{2.5*20.76 }$

$T_b-293k=297.775$

$T_b=590.775k$

Generally the equation for ideal gas is mathematically given by

$PV=nRT$

For v double

$T_c=2*590.775k$

$T_c=1181.55k$

Therefore

$PV=Wbc$

$Wbc=(2.20)(8.314)(1181_590.778)$

$Wbc=10805.7J$

Total Work-done $W_t$

$W_t=Wab+Wbc$

$W_t=0+1.08*10^4$

$W_t=1.08*10^4J$

Generally the equation for amount of heat added is mathematically given by

$Q=nC_p\triangle T$

$Q=2.20*2907*(1181.55-590.775)\\$

$Q=3.778*10^4J$

Generally the equation for change in internal energy of the gas is mathematically given by

$\triangle V=nC_v \triangle T$

$\triangle V=2.20*20.76*(1181.55-293)k$

$\triangle V=4.058*10^4J$

3 0

2 years ago

You can practice converting between the mass of a solution and mass of solute when the mass percent concentration of a solution

vfiekz [6]

Answer:

450. g of 0.173 % KCN solution contains 779 mg of KCN.

Explanation:

Mass of the solution = m

Mass of the KCN in solution = 779 mg

Mass by mass percentage of KCN solution = 0.173%

$(m/m)\%=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$

$0.173\%=\frac{779 mg}{m}\times 100$

$m=\frac{779 mg}{0.173}\times 100= 450,289 mg$

1 mg = 0.001 g

m = 450,289 mg × 0.001 g = 450.289 mg ≈ 450. g

450. g of 0.173 % KCN solution contains 779 mg of KCN.

6 0

2 years ago

What is temperature?

BabaBlast [244]

the degree or intensity of heat present in a substance or object, especially as expressed according to a comparative scale and shown by a thermometer or perceived by touch. So I would have to go with A.

8 0

2 years ago

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