Answer:
10.78 → 4 significant figures, pH = 10.78 → [H⁺] = 1.66ₓ10⁻¹¹ M
6.78 → 3 significant figures, pH = 6.78 → [H⁺] = 1.66ₓ10⁻⁷ M
0.78 → 2 significant figures, pH = 0.78 → [H⁺] = 0.166 M
pH always can be expressed by at least 4 significant figures. The [H⁺], can be expressed by, at least 3 significant figures
Explanation:
Significant figures are the numbers of a measurement that have certainty plus a doubtful number (it is associated with the uncertainty in the measurement). For example, if we measure a paper with a ruler and the ruler measures up to centimeters we can say that the paper is 7.5 cm long, with which we know that the paper is 7 cm + 0.5 cm which we associate with uncertainty. In this case we talk about two significant figures. If the sheet measured 7.57 cm we would already be talking about a more precise measurement and in this case with 3 significant figures.
10.78 → 4 significant figures
6.78 → 3 significant figures
0.78 → 2 significant figures
To determine [H⁺], we apply 10^-pH
10⁻¹⁰°⁷⁸ = 1.66ₓ10⁻¹¹ M
10⁻⁶°⁷⁸ = 1.66ₓ10⁻⁷ M
10⁻⁰°⁷⁸ = 0.166 M
Answer : The total change in enthalpy of this reaction is 25 kJ.
Explanation :
Enthalpy of reaction : It is defined as the changes in heat energy takes place when reactants go to products. It is denotes as .
ΔH = Energy of product - Energy of reactant
ΔH is positive when heat is absorbed and the reaction is endothermic.
ΔH is negative when heat is released and the reaction is exothermic.
In the given potential energy diagram, the energy of product at higher level and energy of reactant at lower level. The ΔH for this reaction will be positive.
Given:
Energy of product = 55 kJ
Energy of reactant = 30 kJ
ΔH = Energy of product - Energy of reactant
ΔH = 55 kJ - 30 kJ
ΔH = 25 kJ
Thus, the total change in enthalpy of this reaction is 25 kJ.
Answer:
445 mL NH₄Br
Explanation:
(Step 1)
Convert grams ammonium bromide (NH₄Br) to moles using its molar mass.
Molar Mass (NH₄Br): 14.007 g/mol + 4(1.008 g/mol) + 79.904 g/mol
Molar Mass (NH₄Br): 97.943 g/mol
8.42 grams NH₄Br 1 mole
----------------------------- x ------------------------ = 0.0860 moles NH₄Br
97.943 grams
(Step 2)
Calculate the volume of NH₄Br using the molarity equation. Then, convert liters (L) to milliliters (mL).
Molarity (M) = moles / volume (L)
0.193 M = 0.0860 moles / volume
(0.193 M) x volume = 0.0860 moles
volume = 0.445 L
1,000 mL = 1 L
0.445 L NH₄Br 1,000 mL
------------------------ x ------------------ = 445 mL NH₄Br
1 L
Number of states present in each band will be equal to total of all the states contributed by N atoms.
For instance, s band will contain N states.
Similarly, a p band will contain 3N states.
Answer:
introducing a radioactive tracer into a sample of pesticide
Explanation:
