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3 years ago

Which explains how burning a magnesium ribbon highlights a toolmark?

Chemistry

1 answer:

Setler [38]3 years ago

6 0

<h2>Answer:</h2>

The magnesium ribbon, <u>D. It forms a material to cast the tool mark</u>.

<h2>Explanation:</h2>

When a magnesium ribbon is burnt in the presence of oxygen it gives out strong light and heat is produced. Apart from it, it leads to the production of substance called as magnesium oxide which is formed as the product due to the reaction of magnesium with the oxygen present in the air.

Tool marks are the mark which is created by tools while using them. In order to identify or locate them castes made up of magnesium oxide is utilized. When this is pasted on the suspected area, the tool mark of the suspected tool gets pasted on it.

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The ka of phosphoric acid, h3po4, is 7.6  10–3 at 25 °c. for the reaction h3po4(aq) h2po4 – (aq) + h+ (aq) ∆h° = –14.2 kj/mol.

blsea [12.9K]

<span>Use the van't Hoff equation: ln ( K2 K1 ) = Î” HÂş R ( 1 T1 â’ 1 T2 ) ln ( K2 7.6*10^-3 ) = -14,200 J 8.314 ( 1 298 â’ 1 333 ) ln ( K2 7.6*10^-3 ) = â’ 1708 ( 0.00035 ) ln ( K2 0.0076 ) = â’ 0.598 Apply log rule a = log b b a -0.598 = ln ( e â’ 0.598 ) = ln ( 1 e 0.598 ) Multiply both sides with e^0.598 K 2 e 0.598 = 0.0076 K e 0.598 e 0.598 = 0.0076 e 0.598 K 2 = 0.0076 e 0.598 = 4.2 â‹… 10 â’ 3 K2 = 4.2 â‹… 10 â’ 3</span>

7 0

3 years ago

What is the [H+] and [OH-] of a 3.5 M HCIO3 solution?

levacccp [35]

Answer: H+ ia helyuim

explinanation: Hope this helped!!

3 0

2 years ago

Combustion reactions are exothermic. The heat of reaction for the combustion of 2-methylheptane, C8H18, is 1.306×103 kcal/mol. W

WARRIOR [948]

Answer:

11.45kcal/g

2.612 × 10³ kcal

Explanation:

When a compound burns (combustion) it produces carbon dioxide and water. The combustion of 2-methylheptane can be represented by the following balanced equation:

2 C₈H₁₈ + 25 O₂ ⇄ 16 CO₂ + 18 H₂O

It releases 1.306 × 10³ kcal every 1 mol of C₈H₁₈ that is burned.

<em>What is the heat of combustion for 2-methylheptane in kcal/gram?</em>

We know that the molar mass of C₈H₁₈ is 114.0g/mol. Then, using proportions:

$\frac{1.306 \times 10^{3}Kcal}{1mol} .\frac{1mol}{114.0g} =11.45kcal/g$

<em>How much heat will be given off if molar quantities of 2-methylheptane react according to the following equation? 2 C₈H₁₈ + 25 O₂ ⇄ 16 CO₂ + 18 H₂O</em>

In this equation we have 2 moles of C₈H₁₈. So,

$2mol \times\frac{1.306 \times 10^{3}kcal }{1mol} =2.612\times 10^{3}kcal$

3 0

2 years ago

Calculate the molality, molarity, and mole fraction of FeCl3 in a 29.5 mass % aqueous solution (d = 1.283 g/mL).

faltersainse [42]

Answer:

molality FeCl3= 2.579 molal

molarity FeCl3 = 2.333 M

mol fraction FeCl3 = 0.0444

Explanation:

Step 1: Data given

Mass % = 29.5 %

Density = 1.283 g/mL

Molar mass FeCl3 = 162.2 g/mol

Step 2: Calculate mass solution

Suppose we have 1L = 1000 mL solution

Mass solution = 1.283 g/mL * 1000 mL = 1283 grams

Step 3: Calculate mass FeCl3

Mass FeCl3 = 0.295 * 1283 grams

Mass FeCl3 = 378.485 grams

Step 4: Calculate mass of water

Mass water = 1283 - 378.485 = 904.515 grams

Step 5: Calculate moles FeCl3

Moles FeCl3 = mass FeCl3 / molar mass FeCl3

Moles FeCl3 = 378.485 grams / 162.2 g/mol

Moles FeCl3 = 2.333 moles

Step 6: Calculate moles H2O

Moles H2O = 904.515 grams / 18.02 g/mol

Moles H2O = 50.195 moles

Step 7: Mol fraction FeCl3

Mol fraction FeCl3 = 2.333 / (50.195+2.333)

Mol fraction FeCl3 = 0.0444

Step 8: Calculate molality

Molality = moles FeCl3 / mass H2O

Molality = 2.333 moles / 0.904515 kg

Molality = 2.579 molal

Step 9: Calculate molarity

Molarity = moles / volume

Molarity FeCl3 = 2.333 moles / 1 L

Molarity FeCl3 = 2.333 M

8 0

3 years ago

A hydrogen bond can occur between:

Readme [11.4K]

A hydrogen bond occurs between a hydrogen from one molecule and an oxygen from another molecule. Option D

<h3>What is the hydrogen bond?</h3>

The hydrogen bond is one that is responsible for association in molecules. It occurs when hydrogen is covalently bonded to a highly electronegative element such as oxygen, nitrogen or Sulphur.

Thus, a hydrogen bond occurs between a hydrogen from one molecule and an oxygen from another molecule. Option D

Learn more about hydrogen bonding:brainly.com/question/10904296?

#SPJ1

5 0

2 years ago