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Harman [31]
3 years ago
12

Which of the following is an irreversible physical change?

Chemistry
1 answer:
Yuliya22 [10]3 years ago
3 0

Answer:

b) sharpening a pencil

Explanation:

If you melt lead, boil water, or dissolve sugar in water, you can return all of them back to their original state. If you sharpen a pencil, you can't reattach the shavings as they were originally.

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What is a niche of a greenfly?
gizmo_the_mogwai [7]

Answer:

Explanation:

Different butterfly species occupy slightly different niches, but most are forest- or field-dwelling, flying, nectar-feeding insects. ... During feeding, butterflies are often covered in pollen, making them effective agents of pollination for plants.

3 0
3 years ago
Which type of equipment would be used to precisely measure 26.0 mL of dilute hydrochloric acid?
VikaD [51]
The type of equipment that would be used to precisely measure 26.0 mL of dilute hydrochloric acid would be C. 50 mL graduated cylinder.
D doesn't have enough mLs to measure this, and A and B have too many. 
8 0
3 years ago
Read 2 more answers
When chemicals react with each other which factors decide that a successful reaction has taken place ?
Elodia [21]

The factors that affect the rate of a reaction are:

  • <em>nature of the reactant</em> - when reactants with different chemical composition are exposed to same conditions they would react differently.  For instance, when an acid or base is added on litmus paper, blue litmus paper turns red in presence of acid while red litmus paper turns blue when base is added.
  • <em>surface area</em>- a compound with small pieces spread over a large area will react faster than a big lump of a compound occupying a small area.
  • <em>temperature of reaction</em>- reactants would react faster at high temperatures. this is because they have higher kinetic energy to collide with each other. Hence a plate of food on the table spoils faster than a plate of food in the fridge.
  • <em>concentration</em>- an increase in concentration leads to more molecules available to collide and form products. An example, when you add more of indicator in a solution, the color becomes more clear since more particles react to give more color.
  • <em>presence of a catalyst</em>- a catalyst lowers the activation energy, which means less energy is required to shift reaction in forward direction. In the presence of iron (Fe) a catalyst, nitrogen N₂ and hydrogen H₂ react to produce NH₃
3 0
3 years ago
How many chiral carbons does the molecule have?
trapecia [35]

Answer:

The molecule has two chiral carbons

Explanation:

i hope its the right answer

7 0
3 years ago
Calculate the amount of HCN that gives the lethal dose in a small laboratory room measuring 12.0 ft×15.0 ft×8.60ft.
garik1379 [7]

<u>Given:</u>

Dimensions of the room= 12 ft * 15 ft * 8.60 ft

<u>To determine:</u>

The amount of HCN that gives the lethal dose in the room with the given dimensions

<u>Explanation:</u>

As per the World Health Organization, the lethal dose of HCN is around 300 ppm

300 ppm = 300 mg of HCN/ kg of inhaled air

Volume of air = volume of room = 12 * 15 *8.6 = 1548 ft³

Now,  1 ft³ = 28316.8 cm³

Therefore, the calculated volume of air corresponds to:

1548 * 28316.8 = 4.383 * 10⁷ cm3

Density of air (at room temperature 25 C) = 0.00118 g/cm3

Thus mass of air corresponding to the calculated volume is

Mass = Density * volume = 0.00118 g/cm3 * 4.383 * 10⁷ cm3

= 5.172*10⁴ g = 51.72 kg

Lethal amount of HCN corresponding to 51.72 kg of air would be.

= 51.72 kg air* 300 mg of HCN/1 kg air = 15516 mg

Ans: Lethal dose of HCN = 15.5 g

7 0
3 years ago
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