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2 years ago

7

calculate the atomic mass of carbon if the two common isotopes of carbon have masses of 12.000 amu (98.89% abundance) and 13.003

amu (1.11% abundance)

1 answer:

Bingel [31]2 years ago

6 0

12.01 amu

Work:

(12.000 × .9889) + (13.003 × .0111) = 12.01

turn the precents into decimals

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Why will frequency decrease when wave gets longer

amid [387]

The frequency will decrease because the waves are getting farther and farther apart and if they and as that happens with shorter and shorter so they decrease

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3 years ago

Solid sodium hydrogen carbonate, NaHCO3, decomposes on heating according to the equation:

tekilochka [14]

Answer:

See explanation

Explanation:

First, let's write the balanced equation again:

2 NaHCO3(s) <-> Na2CO3(s) + H2O(g) + CO2(g)

Now, we know that the total pressure was 7.76 atm. This total pressure, is the sum of the pressure of water and CO2 like this:

Ptotal = Pwat + PCO2 (1)

This is the dalton's law for partial pressures.

The pressure can be also be relationed with the moles

Ratio of mole = Ratio of pressure

so, taking this in consideration we can say the following:

Pwater/PCO2 = moles water / moles CO2

As the only components exerting pressure are CO2 and Water (Because they are in gas phase), the total pressure can be splitted between the two of them so:

Pwater = Ptotal/2

Pwater = 7.76 / 2 = 3.88 atm

With this pressure, and using the ideal gas equation, we can know the moles of water:

PV = nRT

n = PV/RT using R = 0.082 L atm / K mol

n = 3.88 * 5 / 0.082 * (160+273)

n = 0.546 moles of water

b) now that we have the moles of water, we can actually know the moles that reacted originally from the sodium carbonate by stechiometry.

2NaHCO3(s) <-> Na2CO3(s) + H2O(g) + CO2(g) MMCO2 = 84 g/mol

the moles of NaHCO3 initially:

n = 100 / 84

n = 1.19 moles

so, If 1.19 moles of NaHCO3 reacted, and only produces 0.546 moles of water and CO2, then, the remaining moles of NaHCO3 is:

remaining moles = 1.19 - 0.546 = 0.644 moles

therefore the mass remaining:

mCO2 = 0.644 * 84

mCO2 = 54.096 g

c) As it was stated before, only the gaseous components are involved in the pressure, thus, in the kp expression which is:

Kp = Pwater * PCO2

Kp = 3.88 * 3.88

Kp = 15.0544

d) As the total pressure is 7.76 atm and the fact that NaHCO3 is solid, this component is not exerting any pressure in the reaction, as seen in the Kp expression, so it won't matter that if we raise a little the quantity of the reactant, it still has some remaining.

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3 years ago

In an experiment to find the concentration of calcium hydroxide in limewater , 25.0 cm3 of limewater needed 18.8 cm3 of 0.0400 m

Andre45 [30]

Answer:

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2HCl + Ca(OH)2 --> CaCl2 + 2H2O

2 : 1

The relationship between the concentration and volume is given as;

CaVa / CbVb = na / nb

where a = acid (HCl) and b = base Ca(OH)2

Inserting the values;

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nlexa [21]

Answer:

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E = hc/λ

Where h is Planck's constant (6.626*10⁻³⁴ J·s) and c is the speed of light (3*10⁸ m/s).

E = 6.626*10⁻³⁴ J·s * 3*10⁸ m/s ÷ (504*10⁻⁹m) = 3.944 * 10⁻¹⁹ J.

So now we can make the equivalency for this problem, that

<u>1 proton = 3.944 * 10⁻¹⁹ J</u>

Now we convert watts from J/s to proton/s:

1 $\frac{J}{s}*\frac{1proton}{3.944*10^{-19}J}=2.535*10^{18} \frac{proton}{s}$ = 1 W

Solving the problem, a 62 W bulb converts 5% of its output into light, so:

62 * 5/100 = 3.1 W

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LenaWriter [7]

Answer: emission spectrum

Explanation:

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3 years ago