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zhenek [66]
3 years ago
9

Which are exmaples of chemical change?

Chemistry
1 answer:
kifflom [539]3 years ago
7 0

Answer:

cold butter melted when heated, lighting a match, baking cookies,

Explanation:

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The mass of a block is 12 g and the volume is 6 ml. Calculate the density of the block.
HACTEHA [7]

Answer:

According to mass and volume,  block density is 2 g/ml

Explanation:

Density is a measure, usually used in physics and chemistry, that relates the mass and volume of a solid or compound.

In general terms, the density is directly proportional to the mass, and inversely proportional to the volume, so increasing the mass will also increase the density.

The formula used to calculate the density is

ρ = \frac{m}{V}

Therefore, according to the mass and density of the block

ρ = \frac{12}{6} = 2g/ml

Being the density of the block equal to 2 g/ml.

<em>The other options are not possible, because the values given do not correspond to the result of the equation.</em>

5 0
3 years ago
In an accident, a solution containing 2.5 kg of nitric acid was spilled. Two kilograms of Na2CO3 was quickly spread on the area
storchak [24]

First we must write a balanced chemical equation for this reaction

Na_2CO_3 _(_a_q_)+ 2HNO_3_(_a_q_) \implies 2NaNO_3_(_s_) + CO_2_(_g_) + H_2O_(_l_)

The mole ratio for the reaction between HNO_3 and Na_2CO_3 is 1:2. This means 1 moles of Na_2CO_3 will neutralize 2 moles HNO_3. Now we find the moles of each reactant based on the mass and molar mass.

2500g HNO_3 \times \frac{mol}{63.01g\ HNO_3} = 39.67 mol\ HNO_3

2000g\ Na_2CO_3 \times \frac{mol}{105.99g \ Na_2CO_3} = 18.87 mol\ Na_2CO_3

\frac{18.87 mol Na_2CO_3}{39.67\ HNO_3} = \frac{1 molNa_2CO_3}{2 mol HNO_3}

The Na_2CO_3 was enough to neutralize the acid because 18.87:39.67 is the same as 1:2 mol ratio.

4 0
4 years ago
Calculate the weight of 3.491 into 10 to the power 19 molecules of cl2​
Rom4ik [11]

Answer:

The mass of 3.491 × 10¹⁹ molecules of Cl₂  of Cl₂ is 4.11 × 10⁻³ grams

Explanation:

The number of particles in one mole of a substance id=s given by the Avogadro's number which is approximately 6.023 × 10²³ particles

Therefore, we have;

One mole of Cl₂ gas, which is a compound, contains 6.023 × 10²³ individual molecules of Cl₂

3.491 × 10¹⁹ molecules of Cl₂ is equivalent to (3.491 × 10¹⁹)/(6.023 × 10²³) = 5.796 × 10⁻⁵ moles of Cl₂

The mass of one mole of Cl₂ = 70.906 g/mol

The mass of 5.796 × 10⁻⁵ moles of Cl₂ = 70.906 × 5.796 × 10^(-5) = 4.11 × 10⁻³ grams

Therefore;

The mass of 3.491 × 10¹⁹ molecules of Cl₂  of Cl₂ = 4.11 × 10⁻³ grams.

4 0
3 years ago
an alpha particle is identical to a). a neutron b) a helium nucleus c) an electron d) a hydrogen nucleus​
ElenaW [278]

Alpha particles, also called alpha ray or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a <u>helium-4 nucleus. </u>They are generally produced in the process of alpha decay, but may also be produced in other ways.

Composition: 2 protons, 2 neutrons

Mass: 6.644657230(82)×10−27 kg; 4.0015061...

Electric charge: +2 e

Symbol: α, α2+, He2+

3 0
3 years ago
Read 2 more answers
Give an example of an oxidisation reaction!
konstantin123 [22]
<span>When an atom or compound is oxidized, its properties change. For example, when an iron object undergoes oxidation, it is transformed because it has lost electrons. Unoxidized iron is a strong, structurally sound metal, while oxidized iron is a brittle, reddish powder. The diagram below illustrates what happens to an atom of iron as it is oxidized

</span>
4 0
4 years ago
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