The answer is C. The specific amount of energy released when excited electrons fall back to the ground state produces an emission spectrum. That energy is emitted as photons with precise wavelengths corresponding to the energy differences between levels. Because each element yields a characteristic set of wavelengths, the emission spectrum can be used to identify the element in the sample.
1) Calcium carbonate comprises 40.0% calcium by weight.
M(CaCO₃)=100.1 g/mol
M(Ca)=40.1 g/mol
w(Ca)=40.1/100.1=0.400 (which is 40.0%)!
2) The mass fraction mentioned is superfluous information.
3) The resulting solution is:
m(Ca)=1.2 g
m(CaCO₃)=M(CaCO₃)*m(Ca)/M(Ca)
m(CaCO₃)=100.1g/mol*1.2g/40.1g/mol=3.0 g
5060 has three significant figures: Below is the clarification
Explanation:
Significant figures
Significant figures (also referred to as significant digits and decimal places) in a number are those digits that carry substantial meaning.
These include all digits except: leading zeros.
Guidelines for determining significant figures
1. All non-zero digits are counted as significant. For instance, the number 23 has two significant figures.
2. Zeros located between two non-zero digits are significant; for example, 202.1201 contains seven significant figures.
3. Zeros preceding the significant figures are not significant. For example,.000021 has two significant figures, with zeros being non-contributory.
4. Zeros following the significant figures are significant.
This explains why the number 5060 has three significant figures.
The stated condition has been verified. Construct the resonance structure for CSO, where the central atom carries a +2 formal charge and the oxygen atom has a +1 charge. We need to create the resonance structure for CSO as shown in the figure. According to the problem, there is a +2 formal charge on the central atom and a +1 charge on the oxygen atom. The central atom in this structure is sulfur. We will calculate the formal charge of sulfur based on the information presented, demonstrating that it aligns with the necessary formal charges.
A total of 0.0222 moles of NaOH are necessary to react with NH4F. \nBased on the reaction NH4F + NaOH --> NaF + NH3 + H2O, we start with: \nMass of NH4F = 0.821 g, NaOH concentration = 1 M, volume of NaOH = 25 mL. \nTo find moles: moles of NaOH = (CV)/1000. Thus, moles of NaOH = (1 * 25)/1000 = 0.025 moles of NaOH used. \nThe molar mass of NH4F is 37 g/mol, making moles of NH4F = 0.821 / 37 = 0.0222 moles. \nThis shows that NaOH is in excess, with 0.025 - 0.0222 = 0.0028 moles of NaOH remaining. Hence, 0.0222 moles of NaOH are needed to react with NH4F.
