The change in heat is simply equal to:
change in heat ΔH = final enthalpy – initial enthalpy
ΔH = [280.25 g * 4.18J/gC * (17.5°C)] – [280 g * 4.18J/gC
* 13.5°C]
ΔH = 4,699.89 J = 4.7 kJ
<span>Hence heat released is about 4.7 kJ</span>
Answer: D. Roots
Explanation:
Sophie said that the part in question does not belong to an animal. This therefore invalidates options B and C as only animals would have lungs or legs.
Sophie then says that the part does not grow in the direction of light so that removes stems as the correct option because stems grow towards light in order to allow leaves to carry out photosynthesis.
Roots on the other hand grow towards gravity so they grow away from light which means that the correct answer is roots.
Answer:
- <u>C₂H₄</u> (option number 4)
Explanation:
A hydrocarbon with a <em>double bond</em> in its carbon skeleton is an alkene and has the general form:
-
.
This is, the number of hydrogen atoms is twice the number of carbon atoms.
On the other hand, alkanes have only single bonds, and the compounds with a triple bond in its carbon skeleton are alkynes.
Review each choice:
1) <u>C₃H₈:</u>
- In this case, the number of hydrogen atoms is 2×3 + 2 = 6 + 2 = 8, which is corresponds to an alkane, not an alkene.
2)<u> C₂H₆</u>
- For this, the number of hydrogen atoms is 2 × 2 + 2 = 4 + 2 = 6. Again an alkane, not alkene.
3) <u>CH₄</u>
- Hydrogen atoms: 1 × 2 + 2 = 4 ⇒ an alkane
4) <u>C₂H₄ </u>
- Hydrogen atoms: 2 × 2 = 4. This is precisely the relation for an alkene, so this is the hydrocarbon that has a double bond in its carbon skeleton.
- The chemical formula may be writen as CH₂ = CH₂, to show the double bond.
So, this is the correct answer.
5) <u>C₂H₂</u>
- Hydrogen atoms: 2 × 2 - 2 = 4 - 2 = 2. This relation of carbon and hydrogen atoms corresponds to a compound with triple bond, i.e an alkyne: CH≡CH.
Answer:
1.66 × 10⁻¹⁸ Moles
Explanation:
As we know one mole of any substance contains 6.022 × 10²³ particles (atoms, ions, molecules or formula units). This number is also called as Avogadro's Number.
The relation between Moles, Number of Atoms and Avogadro's Number is given as,
Number of Moles = Number of Atoms ÷ 6.022 × 10²³ Atoms/mol
Putting values,
Number of Moles = 1.0 × 10⁶ Atoms ÷ 6.022 × 10²³ Atoms/mol
Number of Moles = 1.66 × 10⁻¹⁸ Moles