For the reaction 2 Cr(s) + 3 Pb²⁺(aq) ⟶ 3 Pb(s) + 2 Cr³⁺(aq), what is the value of n in the Nernst equation?

A forensic chemist is given a white powder for analysis. She dissolves 0.50 g of the substance in 8.0 g of benzene. The solution

Sholpan [36]

Answer:

The given compound cannot be cocaine.

Explanation:

The chemist can comment on the nature of compound being cocaine or not from the depression in freezing point.

Depression in freezing point of is related to molality as:

Depression in freezing point = Kf X molality

Where

Kf = cryoscopic constant = 4.90°C/m

depression in freezing point = normal freezing point - freezing point of solution

depression in freezing point = 5.5-3.9 = 1.6°C

1.6°C = 4.90 X molality

$molality=\frac{1.6}{4.90} = 0.327 m$

we know that:

$molality=\frac{moles}{mass of solvent(kg)}=\frac{moles}{0.008kg}$

therefore

moles = 0.327X0.008 = 0.00261 mol

$moles=\frac{mass}{molarmass}$

$molarmass=\frac{mass}{moles}=\frac{0.50}{0.00261}= 191.57g/mol$

The molar mass of cocaine is 303.353

So the given compound cannot be cocaine.

3 0

3 years ago

How many grams of Ni are formed from 55.3 g of Ni2O3? 2Ni2O3(s)⟶4Ni(s)+3O2(g)

Neko [114]

Answer:

39.2 g

Explanation:

2Ni₂O₃(s) ⟶ 4Ni(s) + 3O₂(g)

First we convert 55.3 grams of Ni₂O₃ into moles of Ni₂O₃, using its molar mass:

55.3 g ÷ 165.39 g/mol = 0.334 mol Ni₂O₃

Then we convert 0.334 moles of Ni₂O₃ into moles of Ni, using the stoichiometric coefficients of the balanced reaction:

0.334 mol Ni₂O₃ * $\frac{4molNi}{2molNi_2O_3}$ = 0.668 mol Ni

Finally we calculate how much do 0.668 Ni moles weigh, using the molar mass of Ni :

0.668 mol Ni * 58.69 g/mol = 39.2 g

7 0

3 years ago

A 2.026g sample of a hydrate of sodium carbonate (Na2CO3) is heated to remove water. After heating, the mass of the sample is 0.

OLEGan [10]

Answer:

62.98 % of the sample of hydrate is water

Explanation:

Step 1: Data given

Mass of the sample of a hydrate of sodium carbonate (Na2CO3) = 2.026 grams

After heating, the mass of the sample is 0.750 g

Molar mass H2O = 18.02 g/mol

Step 2: Calculate mass of water

Mass water = mass of hydrate - mass of sample after heating

Mass water = 2.026 grams - 0.750 grams

Mass water = 1.276 grams

Step 3: Calculate mass % percent of water

Mass % of water = (mass of water / total mass hydrate) * 100 %

Mass % of water = (1.276 grams / 2.026 grams) *100 %

Mass % of water = 62.98 %

62.98 % of the sample of hydrate is water

7 0

3 years ago

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I have to do this for homework please help :)

kramer

Answer:

1..... nucleus

2......electron cloud

3.......protons

4........Neutrons

5..........electron

6............electrons

7...............Isotopes

8.....,...........ions

9....................charge

6 0

3 years ago

Part A:

uranmaximum [27]

Answer:

Part A = The mass of sulfur is 6.228 grams

Part B = The mass of 1 silver atom is 1.79 * 10^-22 grams

Explanation:

Part A

Step 1: Data given

A mixture of carbon and sulfur has a mass of 9.0 g

Mass of the product = 27.1 grams

X = mass carbon

Y = mass sulfur

x + y = 9.0 grams

x = 9.0 - y

x(molar mass CO2/atomic mass C) + y(molar mass SO2/atomic mass S) = 22.6

(9 - y)*(44.01/12.01) + y(64.07/32.07)

(9-y)(3.664) + y(1.998)

32.976 - 3.664y + 1.998y = 22.6

-1.666y = -10.376

y = 6.228 = mass sulfur

x = 9.0 - 6.228 = 2.772 grams = mass C

The mass of sulfur is 6.228 grams

Part B

Calculate the mass, in grams, of a single silver atom (mAg = 107.87 amu ).

Calculate moles of 1 silver atom

Moles = 1/ 6.022*10^23

Moles = 1.66*10^-24 moles

Mass = moles * molar mass

Mass = 1.66*10 ^-24 moles *107.87

Mass = 1.79 * 10^-22 grams

The mass of 1 silver atom is 1.79 * 10^-22 grams

5 0

2 years ago

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