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2 years ago

Explain how you can determine the number of protons electrons and neutrons an atom has by its mass number and atomic number

1 answer:

8 0

The number of n protons can be easily determined by its atomic number. With the atomic number and mass number (rounded If not already), then with basic subtraction we can calculate the number of neutrons...
Hope that helped!

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You mix 285.0 mL of 1.20 M lead(II) nitrate with 300.0 mL of 1.60 M potassium iodide. The lead(II) iodide is insoluble. Which of

SIZIF [17.4K]

Answer:

D. The final concentration of NO3– is 0.821 M.

Explanation:

Considering:

$Molarity=\frac{Moles\ of\ solute}{Volume\ of\ the\ solution}$

Or,

$Moles =Molarity \times {Volume\ of\ the\ solution}$

Given :

For potassium iodide :

Molarity = 1.60 M

Volume = 300.0 mL

The conversion of mL to L is shown below:

1 mL = 10⁻³ L

Thus, volume = 300.0×10⁻³ L

Thus, moles of potassium iodide :

$Moles=1.60 \times {300.0\times 10^{-3}}\ moles$

Moles of potassium iodide = 0.48 moles

For lead(II) nitrate :

Molarity = 1.20 M

Volume = 285 mL

The conversion of mL to L is shown below:

1 mL = 10⁻³ L

Thus, volume = 285×10⁻³ L

Thus, moles of lead(II) nitrate :

$Moles=1.20\times {285\times 10^{-3}}\ moles$

Moles of lead(II) nitrate = 0.342 moles

According to the given reaction:

$2KI_{(aq)}+Pb(NO_3)_2_{(aq)}\rightarrow PbI_2_{(s)}+2KNO_3_{(aq)}$

2 moles of potassium iodide react with 1 mole of lead(II) nitrate

1 mole of potassium iodide react with 1/2 mole of lead(II) nitrate

0.48 moles potassium iodide react with 0.48/2 mole of lead(II) nitrate

Moles of lead(II) nitrate = 0.24 moles

Available moles of lead(II) nitrate = 0.342 moles

Limiting reagent is the one which is present in small amount. Thus, potassium iodide is limiting reagent.

Also, consumed lead(II) nitrate = 0.24 moles (lead ions precipitate with iodide ions)

Left over moles = 0.342 - 0.24 moles = 0.102 moles

Total volume = 300 + 285 mL = 585 mL = 0.585 L

So, Concentration = 0.102/0.585 M = 1.174 M

Statement A is correct.

The formation of the product is governed by the limiting reagent. So,

2 moles of potassium iodide gives 1 mole of lead(II) iodide

1 mole of potassium iodide gives 1/2 mole of lead(II) iodide

0.48 mole of potassium iodide gives 0.48/2 mole of lead(II) iodide

Mole of lead(II) iodide = 0.24 moles

Molar mass of lead(II) iodide = 461.01 g/mol

Mass of lead(II) chloride = Moles × Molar mass = 0.24 × 461.01 g = 111 g

Statement B is correct.

Potassium iodide is the limiting reagent. So all the potassium ion is with potassium nitrate . Thus,

2 moles of Potassium iodide on reaction forms 2 moles of potassium ion

0.48 moles of Potassium iodide on reaction forms 0.48 moles of potassium ion

Total volume = 300 + 285 mL = 585 mL = 0.585 L

So, Concentration = 0.48/0.585 M = 0.821 M

Statement C is correct.

Nitrate ions are furnished by lead(II) nitrate . So,

1 mole of lead(II) nitrate produces 2 moles of nitrate ions

0.342 mole of lead(II) nitrate produces 2*0.342 moles of nitrate ions

Moles of nitrate ions = 0.684 moles

So, Concentration = 0.684/0.585 M = 1.169 M

Statement D is incorrect.

4 0

2 years ago

The measured value 24.00 g has an uncertainty of?

Orlov [11]

Answer:

±0.005 g

Explanation:

The uncertainty depends on whether the measurement was obtained manually or digitally.

1. Manual

The minimum uncertainty is ±0.01 g.

It may be greater, depending on random or personal errors

2. Digital

Most measurements of mass are now made on digital scales.

A digital device must always round off the measurement it displays.

For example, if the display reads 20.00, the measurement must be between 20.005 and 19.995 (±0.005).

If the measured value were 20.006, the display would round up to 20.01.

If the measured value were 19.994, the display would round down to 19.99.

The uncertainty is ±0.005 g.

The scale shown below would display a mass of 20.00 g

6 0

3 years ago

What is a photon?

vlabodo [156]

Answer:

Explanation:

try it I'm 60%sur its this

8 0

2 years ago

Why are enzymes important to cells? They help bring about chemical reactions. They provide structural support. They form the two

topjm [15]

They help bring about chemical reactions. This is because enzymes act as catalysts, lowering the activation energy required for a chemical reaction to initiate. It is in this way that they bring about chemical reactions.

4 0

2 years ago

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Please help me out with this question if you help me I will give you the brain thing and extra points. 8/9 image below.

Nataly [62]

Answer:

the answer is most likely b, sorry if im wrong.

Explanation:

.....

7 0

2 years ago

Read 2 more answers