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Alborosie
3 years ago
7

Select the correct answer from each drop-down menu.

Chemistry
2 answers:
seraphim [82]3 years ago
5 0

1. protons and neutrons

2. electrons

liraira [26]3 years ago
4 0

Answer:

Protons and neutrons, Electrons

Explanation:

Protons and electrons are found in the center of the nucleus. The atomic mass is the summation of the number of neutrons and protons.  Electrons orbit around the nucleus in an atom. The atomic number is equal to the number of electrons which is also equal to the number of protons.

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A little aluminum boat (mass of 14.50
Valentin [98]
When the volume is 450 cm3 so the boat will displace 450 g.

so we have  450 g - 14.5g = 435.5 left 

so to get how many pennies can be added to the boat before it sinks can be determined by:

divided the mass for the one penny:

no.of Penny = 435.5 / 2.5g

                     = 174.2 

∴ the boat will float with 174 pennies and will start to sink with 175 

5 0
3 years ago
At 63.5 C the vapor pressure of H2O is 175 torr and that of ethanol is 400 torr. A solution is made by adding equal masses of H2
xxTIMURxx [149]

Answer:

Moel fraction of ethanol in the solution = 0.28

Vapor pressure of the solution = 238 torr

Mole fraction of ethanol in the vapor = 0.47

Explanation:

Let's use 100 g of each substance as a calculus basis. Knowing that the molar mass of water is 18 g/mol and the molar mass of ethanol is 46 g/mol, the number of moles (n = mass/molar mass) of each one is:

nw = 100/18 = 5.56 mol

ne= 100/46 = 2.17 mol

The total number of moles is 7.73 mol, so the mole fraction of ethanol is

2.17/7.73 = 0.28

The mole fraction of water must be 0.72, so if we assume that the solution is ideal, by the Raoult's law, the solution vapor pressure is the sum of the multiplication of the mole fraction by the vapor pressure of each substance, thus:

P = 0.28*400 + 0.72*175

P = 238 torr

The partial pressure of each substance can be found by the multiplication of the molar fraction by the vapor pressure, thus:

Pw = 0.72*175 = 126 torr

Pe = 0.28*400 = 112 torr

To know the number of moles that is vaporized above the solution, we may use the ideal gas law:

PV = nRT

P/n = RT/V

R is the gas constant, T is the temperature and V is the volume, so they are the same for both water and ethanol, thus

Pw/nw = Pe/ne

126/nw = 112/ne

ne = (112/126)*nw

ne = 0.89nw

So, the mole fraction of ethanol is:

ne/(ne + nw) = 0.89nw/(0.89nw + nw) = 0.89/1.89 = 0.47

4 0
3 years ago
When electromagnetic radiation of wavelength 300nm falls on the surface of sodium electrons are emitted with a KE of 1.68 * 10 5
gtnhenbr [62]

Answer:

3.83 × 10⁻¹⁹ J;  518 nm  

Step-by-step explanation:

The equation for the <em>photoelectric effect</em> is

hf = Φ + KE  

<em>Data: </em>

λ = 300 nm = 300 × 10⁻⁹ m

KE = 1.68 × 10⁵ J/mol

Calculations:

Part 1. Minimum energy to remove an electron

(a) Calculate the <em>energy of the photon</em>

fλ = c  

 f = c/λ     Divide each side by λ

E = hf

E = hc/λ

E = (6.626× 10⁻³⁴ × 2.998 × 10⁸)/(300 × 10⁻⁹)

E = 6.622 × 10⁻¹⁹ J

(b) Calculate the <em>KE of one electron</em>

KE = 1.68 × 10⁵ × 1/(6.022 × 10²³)

KE = 2.790 × 10⁻¹⁹ J

(c) Calculate the work function

hf = Φ + KE     Subtract KE from each side

Φ = 6.622 × 10⁻¹⁹  - 2.790 × 10⁻¹⁹

Φ = 3.83 × 10⁻¹⁹ J

The minimum energy to remove an electron from a sodium atom

is 3.83 × 10⁻¹⁹ J.

Part 2. Maximum wavelength to remove an electron

The photon must have just enough energy to overcome the work function and leave the electron with zero kinetic energy.

    E = Φ

hc/λ = Φ                      Multiply each side by λ

  hc = Φ λ                   Divide each side by Φ

   λ = hc/ Φ

   λ = (6.626 × 10⁻³⁴ × 2.998 × 10⁸)/(3.83 × 10⁻¹⁹)

   λ = 5.18 × 10⁻⁷ m     Convert to nanometres

   λ = 518 nm

The maximum wavelength that will cause an electron to move is 518 nm.

6 0
3 years ago
Read 2 more answers
Which of the aqueous solution does not conduct electricity ? 1.Ca(NO3)2 / 2.CH3NH2/ 3.CH3OH/ 4.CH3COOH
bezimeni [28]

For an aqueous solution to conduct electricity, ions must be present in solution.

This means soluble salts will conduct electricity. Also, since acids and bases have ions in solution, they could also conduct electricity. Option 1 is a soluble salt. Options 2 and 4 are base and acid respectively. Option 3, though soluble in water, exist as a molecule, therefore its solution cannot conduct electricity.

8 0
3 years ago
If 62.3 mL of lead(II) nitrate solution reacts completely with excess sodium iodide solution to yield 0.862 g of precipitate, wh
Alexxx [7]

Answer:

The molarity of the lead(II) ion in the original solution is 0.03M

Explanation:

<u>Step 1:</u> The balanced reaction

Pb(NO3)2(aq) + 2 NaI aq) → PbI2(s) + 2 NaNO3 (aq)

Pb2+ + 2I- →PbI2

This means that for 1 mole Pb2+ consumed, there is needed 2 moles of I- to produce 1 mole of PbI2

<u>Step 2:</u> Calculate moles of PbI2

Moles of PbI2 = 0.862g / 461.01 g/mole

moles of PbI2 = 0.00187 moles

<u>Step 3:</u> calculate moles of Pb2+

For 1 mole of PbI2 produced we need 1 mole of Pb2+

This means for 0.00187 moles of PbI2 we need 0.00187 moles of Pb2+

<u>Step 4:</u> Calculate the molarity of the Pb2+ ion

Molarity of Pb2+ = moles of Pb2+ / volume =

Molarity of Pb2+ = 0.00187 moles / 62.3*10^-3

Molarity of Pb2+ ion = 0.03M

The molarity of the lead(II) ion in the original solution is 0.03M

5 0
3 years ago
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