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tatuchka [14]
3 years ago
15

What methods do scientists use to determine if a change was physical or chemical?

Chemistry
1 answer:
Bess [88]3 years ago
5 0
A physical change will not change the chemical make-up of the material. the change will not produce a new substance.

a chemical change will have a reaction that produces heat, light, a change in color, releases a gas, or rust
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For each pair below, select the sample that contains the largest number of moles. Pair A 2.50 g O2 2.50 g N2
raketka [301]

Answer:

Explanation:

Pair  2.50g of O₂ and 2.50g of  N₂

The atoms sample with the largest number of moles since the masses are the same would be the one with lowest molar mass according the the equation below:

Number of moles = \frac{mass }{molarmass}

Atomic mass of O = 16g and N = 14g

Molar mass of O₂ = 16 x 2 = 32gmol⁻¹

Molar mass of N₂ = 14 x 2 = 28gmol⁻¹

Number of moles of O₂ = \frac{2.5}{32} = 0.078mole

Number of moles of N₂ = \frac{2.5}{28} =  0.089mole

We see that N₂ has the largest number of moles

4 0
3 years ago
Read 2 more answers
2.A calibration curve requires the preparation of a set of known concentrations of CV, which are usually prepared by dieting a s
Aleks04 [339]

Answer:

In order to prepare 10 mL, 5 μM; <em> 2 mL of the 25 μM stock solution will be taken and diluted with water up to 10 mL mark.</em>

In order to prepare 10 mL, 10 μM; <em>4 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

In order to prepare 10 mL, 15 μM; <em>6 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

In order to prepare 10 mL, 20 μM; <em>8 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

Explanation:

Using the dilution equation:

no of moles before dilution = no of moles after dilution.

Molarity x volume (initial)= Molarity x volume (final).

In order to prepare 10 mL, 5 μM from 25 μM solution,

Final molarity = 5 μM, final volume = 10 mL, initial molarity = 25 μM, initial volume = ?

25 x initial volume = 5 x 10

Initial volume = 50/25

                       = 2 mL

<em>2 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

<em />

In order to prepare 10 mL, 10 μM from 25 μM stock,

25 x initial volume = 10 x 10

Initial volume = 100/25 = 4 mL

<em>4 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

In order to prepare 10 mL, 15 μM from 25 μM stock,

25 x initial volume = 15 x 10

initial volume = 150/25 = 6 mL

<em>6 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

In order to prepare 10 mL, 20 μM from 25 μM stock,

25 x initial volume = 20 x 10

initial volume = 200/25 = 8 mL

<em>8 mL of the 25 μM stock solution will be taken and diluted up to 10 mL mark.</em>

6 0
3 years ago
What are the compounds empirical and molecular formulas
Liono4ka [1.6K]

Answer:

The empirical formula is the simplest ratio of atoms while molecular is the actual formula.

Explanation:

Empirical Formula is the simplest ratio of atoms present in the compound.

The molecular formula shows the actual number of atoms present in the compound.

For example, CH is the empirical formula and C6H6 is the molecular formula of benzene.

5 0
2 years ago
Given the balanced equation, how many moles of sulfur trioxide are produced from 160 grams of oxygen ?
pickupchik [31]

I believe this topic is quantitative chemistry but I need the equation to work this out sorry

3 0
3 years ago
In a video game a flying cocunut moves
Delvig [45]

Answer:

In a video game, a flying coconut moves at a constant velocity of 20 meters/second. The coconut hits an obstacle and moves in the opposite direction with a constant velocity of 10 meters/second.

Explanation:

8 0
3 years ago
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