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I am Lyosha [343]
3 years ago
5

Please help chemistry timed test

Chemistry
2 answers:
Artist 52 [7]3 years ago
8 0

Answer:

Barrium nucleus has 56 protons and 137−56=81 neutrons.

Atomic Mass 137.327 atomic mass units

Number of Protons 56

Number of Neutrons 81

Number of Electrons 56

lakkis [162]3 years ago
7 0

Answer:

54

Barium atomic number is 56, this means that it has 56 protons in its nucleus and put it as a period 6 element. an uncharged barium atom would have 56 electron also. However as a group 2 element barium easily loses 2 electron to form the +2 cation. the ions has 56-2=54

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How many atoms of gold are in gold nugget with a mass of 4.25 g
Feliz [49]
Number of Atoms in Gold for given mass can be calculated using following formula,

              # of Moles  =  Number of Atoms / 6.022 × 10²³
Or,
             Number of Atoms  =  Moles × 6.022 × 10²³     ------- (1)    

Calculating Moles,
As,
                              Moles  =  Mass / M.mass
So,
                              Moles  =  4.25 g / 196.96 g/mol

                              Moles  =  0.0215

Putting value of mole in eq.1,

             Number of Atoms  =  0.0215 × 6.022 × 10²³

             Number of Atoms  =  1.299 × 10²²

Result:
            4.25 g 
of Gold Nugget contains 1.299 × 10²² Atoms.
3 0
3 years ago
Read 2 more answers
Joebert had a rectangular cup and filled it with water. He measured the water's mass and volume. Then he got a density of 1.25g/
ANTONII [103]

Answer:

Percent error = 25%

Explanation:

Given data:

Measured density of water = 1.25 g/mL

Accepted density value of water = 1 g/mL

Percent error = ?

Solution:

Formula:

Percent error = (measured value - accepted value / accepted value) × 100

Now we will put the values in formula:

Percent error = (1.25 g/mL - 1 g/mL /1 g/mL )× 100

Percent error = (0.25 g/mL /1 g/mL )× 100

Percent error = 0.25 × 100

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5 0
3 years ago
To a 25.00 mL volumetric flask, a lab technician adds a 0.150 g sample of a weak monoprotic acid, HA , and dilutes to the mark w
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<u>Answer:</u> The number of moles of weak acid is 4.24\times 10^{-3} moles.

<u>Explanation:</u>

To calculate the moles of KOH, we use the equation:

\text{Molarity of the solution}=\frac{\text{Moles of solute}}\text{Volume of solution (in L)}}

We are given:

Volume of solution = 43.81 mL = 0.04381 L      (Conversion factor: 1L = 1000 mL)

Molarity of the solution = 0.0969 moles/ L

Putting values in above equation, we get:

0.0969mol/L=\frac{\text{Moles of KOH}}{0.04381}\\\\\text{Moles of KOH}=4.24\times 10^{-3}mol

The chemical reaction of weak monoprotic acid and KOH follows the equation:

HA+KOH\rightarrow KA+H_2O

By Stoichiometry of the reaction:

1 mole of KOH reacts with 1 mole of weak monoprotic acid.

So, 4.24\times 10^{-3}mol of KOH will react with = \frac{1}{1}\times 4.24\times 10^{-3}=4.24\times 10^{-3}mol of weak monoprotic acid.

Hence, the number of moles of weak acid is 4.24\times 10^{-3} moles.

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