Answer: C
Explanation:
In endothermic reactions, enthalpy is positive, and in exothermic reactions, enthalpy is negative, So, if enthalpy is positive, then it is an endothermic reaction, and hence is required for the reaction to occur.
Answer:
A. 266g/mol
Explanation:
A colligative property of matter is freezing point depression. The formula is:
ΔT = i×Kf×m <em>(1)</em>
Where:
ΔT is change in temperature (0°C - -0,14°C = 0,14°C)i is Van't Hoff factor (1 for a nonelectrolyte dissolved in water), kf is freezing point molar constant of solvent (1,86°Cm⁻¹) and m is molality of the solution (moles of solute per kg of solution). The mass of the solution is 816,0g
Replacing in (1):
0,14°C = 1×1,86°Cm⁻¹× mol Solute / 0,816kg
<em>0,0614 = mol of solute</em>.
As molar mass is defined as grams per mole of substance and the compound weights 16,0g:
16,0g / 0,0614 mol = 261 g/mol ≈ <em>A. 266g/mol</em>
I hope it helps!
The correct answers from the choices are:
a. Reduce inflammation locally
b. Antagonize H1 receptors
c. May be administered orally
<span>d. Are systemically distributed
</span><span>Antihistamines are drugs that are H1 antagonists or blockers, may be administered orally, are distributed systemically, and do not directly reduce nasal congestion.</span>
Answer is: (3) ionic and molecular.
Ionic compounds are made of ions held together with ionic bonds.
Ionic bond forms when a cation transfers its extra electron to an anion who needs it.
For example compound magnesium chloride (MgCl₂) has ionic bond (the electrostatic attraction between oppositely charged ions).
Magnesium (metal) transfers two electrons (became positive cation) to chlorine (became negative anion).
Molecular compounds are made up of molecules whose atoms are connected with covalent bonds.
Covalent bond is bond between nonmetals.
For example, molecule carbon monoxide CO has covalent bond.
Carbon (C) and oxygen (O) are nonmetals.
Carbon atom and oxygen atom are connected by a triple bond (six shared electrons in three bonding molecular orbitals) that is formed of two covalent bonds and one dative covalent bond.
869.6 × 10¹⁴ molecules of EDB
Explanation:
We have 1.9 lb of flour with a EDB concentration of 31.5 ppb.
We need to transform lb in grams.
1 lb = 453.6 grams
1.9 lb = (1.9 × 453.6) / 1 = 861.8 grams
Now we determine the number of molecules of EDB in the sample by devise the following reasoning:
if we have 31.5 × 10⁻⁹ g of EDB in 1 g of sample
then we have X g of EDB in 861.8 g of sample
X = (31.5 × 10⁻⁹ × 861.8) / 1 = 27146.7 × 10⁻⁹ g of EDB
Molecular mass of EDB (C₂H₄Br₂) = 188 g/mole
Taking in account that 1 mole of any substance contains 6.022 × 10²³ (Avogadro’s number) molecules we devise the following reasoning:
if 188 g of EDB contains 6.022 × 10²³ molecules
then 27146.7 × 10⁻⁹ g of EDB contains Y molecules
Y = (27146.7 × 10⁻⁹ × 6.022 × 10²³) / 188 = 869.6 × 10¹⁴ molecules of EDB
Learn more:
about Avogadro’s number
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