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Tju [1.3M]
3 years ago
7

A chemist who studies water samples did a demonstration of how to test for lead in water. She added a clear solution of potassiu

m iodide to a clear solution of lead nitrate. Then a yellow swirling solid formed in the liquid. What is most likely true about the yellow solid?
Chemistry
2 answers:
evablogger [386]3 years ago
8 0

<em>I actually need help myself with question and no one has helped me yet ? </em>

Lerok [7]3 years ago
3 0

Answer:

The swirling yellow solid formed is lead iodide (PbI₂).

Explanation:

  • The reaction of potassium iodide (KI) with lead nitrate (Pb(NO₃)₂) will produce lead iodide (PbI₂) and potassium nitrate (KNO₃) according to the equation:

2KI + Pb(NO₃)₂ → PbI₂↓ + 2KNO₃

  • Lead iodide (PbI₂) is a yellow swirling precipitate that is formed from the reaction.
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Perform the calculation and record the answer with the correct number of significant figures.
kotykmax [81]

The question is incomplete, here is the complete question:

A. (6.5-6.10)/3.19

B. (34.123 + 9.60) / (98.7654 - 9.249)

<u>Answer:</u>

<u>For A:</u> The answer becomes 0.1

<u>For B:</u> The answer becomes 0.4884

<u>Explanation:</u>

Significant figures are defined as the figures present in a number that expresses the magnitude of a quantity to a specific degree of accuracy.

Rules for the identification of significant figures:

  • Digits from 1 to 9 are always significant and have infinite number of significant figures.
  • All non-zero numbers are always significant. For example: 664, 6.64 and 66.4 all have three significant figures.
  • All zeros between the integers are always significant. For example: 5018, 5.018 and 50.18 all have four significant figures.
  • All zeros preceding the first integers are never significant. For example: 0.00058 has two significant figures.
  • All zeros after the decimal point are always significant. For example: 2.500, 25.00 and 250.0 all have four significant figures.
  • All zeroes used solely for spacing the decimal point are not significant. For example: 10000 has one significant figure.

<u>Rule applied for addition and subtraction:</u>

The least precise number present after the decimal point determines the number of significant figures in the answer.

<u>Rule applied for multiplication and division:</u>

In case of multiplication and division, the number of significant digits is taken from the value which has least precise significant digits

  • <u>For A:</u> (6.5-6.10)/3.19

This a a problem of subtraction and division.

First, the subtraction is carried out.

\Rightarow \frac{6.5-6.10}{3.19}=\frac{0.4}{3.19}

Here, the least precise number after decimal was 1.

\Rightarrow \frac{0.4}{3.19}=0.125

Here, the least precise number of significant digit is 1. So, the answer becomes 0.1

  • <u>For B:</u> (34.123 + 9.60) / (98.7654 - 9.249)

This a a problem of subtraction, addition and division.

First, the subtraction and addition is carried out.

\Rightarow \frac{34.123+9.60}{98.7654-9.249}=\frac{43.723}{89.5164}=\frac{43.72}{89.516}

Here, the least precise number after decimal in addition are 2 and in subtraction are 3

\Rightarrow \frac{43.72}{89.516}=0.48840

Here, the least precise number of significant digit are 4. So, the answer becomes 0.4884

6 0
3 years ago
A flask with vinegar in it has a mass of 160 grams. a balloon with baking soda in it has a mass of 40 grams. the balloon is atta
Rashid [163]
Following the Law of Conservation of Mass, you simply add the mass of both substances. Thus, 160 grams + 40 grams = 200 grams. So, even if initially, they are in liquid and solid form, they would still have the same mass even if they change phases, owing to that they are in a closed space.
8 0
3 years ago
Read 2 more answers
If a 32.5 mL of a 15.1 M HCl solution was diluted to 3.25 L with water, what is the final concentration?
user100 [1]

Answer:

The final concentration is 0,151 M.

Explanation:

A dilution consists of the decrease of concentration of a substance in a solution (the higher the volume of the solvent, the lower the concentration).

We convert the unit of volume in L into ml: 3,25 x 1000= 3250 ml

We use the formula for dilutions:

C1 x V1 = C2 x V2

C2= (C1 xV1)/V2

C2= (32, 5 ml x 15, 1 M)/ 3250 ml

<em>C2=0,151 M</em>

8 0
3 years ago
How is the periodic table arranged ( give two ways)
vlabodo [156]
Left side metals right side non metals. arrganged in groups (columns) and periods (rows), each group tells you amount of valence electrons
7 0
3 years ago
Consider the exothermic reaction
alisha [4.7K]

Answer:

The answer to your question is -2855 J

Explanation:

Reaction

                     2C₂H₆  +  7O₂   ⇒   4CO₂  +  6H₂O

Formula

Heat of reaction = ΔHrxn = ΣΔHrxn products - ΣΔHrxn reactants

Substitution

ΔHrxn = { 4(-393.5) + 6(-241.8)} - {2(-84.7) + 7(0)}

ΔHrxn = {-1574 -1450.8} - {-169.4}

ΔHrxn = -3024.8 + 169.4

ΔHrxn = -2855.4 J

4 0
3 years ago
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