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3 years ago

Which two observations are evidence that a chemical change is happening?

Chemistry

1 answer:

UNO [17]3 years ago

8 0

B. Bubbles are created whether using heat or not at inception of chemical change

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PLSS HELP ASAP PLSS

Zepler [3.9K]

molar concentration of Na⁺ ions = 3 M

molar concentration of CO₃⁻ ions = 1.5 M

First the water will solvate the sodium carbonate (Na₂CO₃).

Second the 80 mL of water added will dilute the first solution.

Explanation:

When you dissolve the Na₂CO₃ in water, the following solvation process takes place:

Na₂CO₃ (s) + H₂O (l) → 2 Na⁺ (aq) + CO₃⁻ (aq)

To find the final concentration of Na₂CO₃ solution we use the following formula:

concentration (1) × volume (1) = concentration (2) × volume (2)

concentration (2) = concentration (1) × volume (1) / volume (2)

concentration of Na₂CO₃ solution = 2.5 M × 120 mL / 200 mL

concentration of Na₂CO₃ solution = 1.5 M

molar concentration = number of moles / volume (L)

number of moles = molar concentration × volume (L)

number of moles of Na₂CO₃ = 1.5 M × 0.2 L = 0.3 moles

Knowing the solvation process we devise the following reasoning:

if 1 mole of Na₂CO₃ produces 2 moles of Na⁺ ions and 1 mole of CO₃⁻ ions

then 0.3 moles of Na₂CO₃ produces X moles of Na⁺ ions and Y mole of CO₃⁻ ions

X = (0.3 × 2) / 1 = 0.6 moles of Na⁺ ions

Y = (0.3 × 1) / 1 = 0.3 moles of CO₃⁻ ions

molar concentration = number of moles / volume (L)

molar concentration of Na⁺ ions = 0.6 / 0.2 = 3 M

molar concentration of CO₃⁻ ions = 0.3 / 0.2 = 1.5 M

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molar concentration

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6 0

3 years ago

A metallic substance separates into different metals when heated to certain temperatures. This substance may be an

MariettaO [177]

Answer:

The substance may be an alloy

7 0

3 years ago

According to the law of conservation of matter, the number of ________ is not changed by a chemical reaction.

Taya2010 [7]

According to the law of conservation of matter, the number of Atoms<span> is not changed by a chemical reaction.
</span><span>

They're the same before and after a chemical reaction</span>

4 0

3 years ago

Read 2 more answers

Which mixtures cannot be separated by magnet?

frutty [35]

Answer:
mixtures containing substances
Explanation:
# Carry on learning

4 0

3 years ago

What is the empirical formula of a compound which contains 84.4% c and 15.6% h by mass?

podryga [215]

Answer: The empirical formula for the given compound is $CH_2$

Explanation : Given,

Percentage of C = 84.4 %

Percentage of H = 15.6 %

Let the mass of compound be 100 g. So, percentages given are taken as mass.

Mass of C = 84.4 g

Mass of H = 15.6 g

To formulate the empirical formula, we need to follow some steps:

Step 1: Converting the given masses into moles.

Moles of Carbon = $\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=\frac{84.4g}{12g/mole}=7.03moles$

Moles of Hydrogen = $\frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=\frac{15.6g}{1g/mole}=15.6moles$

Step 2: Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is 7.03 moles.

For Carbon = $\frac{7.03}{7.03}=1$

For Hydrogen = $\frac{15.6}{7.03}=2.22\approx 2$

Step 3: Taking the mole ratio as their subscripts.

The ratio of C : H = 1 : 2

Hence, the empirical formula for the given compound is $C_1H_2=CH_2$

7 0

3 years ago