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Chapter 1: Problem 46

You are given a sample of a silvery metal. What information could you use to prove the metal is silver?

Short Answer

Expert verified
Check visual appearance, calculate density, test conductivity, perform chemical tests, and use XRF analysis to verify if the metal is silver.

Step by step solution

01

Visual Inspection

Examine the physical appearance of the metal. Silver has a distinctive, shiny, silvery-white color. Check for signs of tarnish, which can indicate oxidation, as silver tends to tarnish over time when exposed to air.
02

Density Check

Measure the mass and the volume of the metal sample to calculate its density using the formula \( \text{Density} = \frac{\text{Mass}}{\text{Volume}} \). The density of silver is approximately 10.49 g/cm鲁. Compare the calculated density to this value to see if they match.
03

Conductivity Test

Test the electrical conductivity of the metal. Pure silver is the best conductor of electricity among metals. Use an ohmmeter to measure the resistance across the metal; lower resistance indicates higher conductivity consistent with silver.
04

Chemical Test

Perform a chemical test using nitric acid and potassium dichromate. Silver will dissolve in nitric acid, forming a clear silver nitrate solution. Adding potassium dichromate to this solution will cause a red solid (silver chromate) to precipitate if the metal is silver.
05

Use X-ray Fluorescence (XRF)

Use X-ray fluorescence (XRF) analysis to determine the composition of the metal. Silver will show strong peaks at specific wavelengths characteristic of silver.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Density Measurement
To identify a silver metal, one common method involves measuring its density. Density is defined as mass per unit volume, expressed using the formula: \[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \]Silver has a known density of about 10.49 g/cm鲁. To determine if your sample is silver, follow these steps:
  • Measure the mass of the metal using a precise scale.
  • Determine the volume by displacement of water or by using geometrical calculations, if the sample shape allows.
  • Calculate the density using the measured mass and volume.
Compare your calculated density to 10.49 g/cm鲁. A close match suggests the sample could indeed be silver.
Electrical Conductivity Test
Electrical conductivity tests can help confirm if a metal is silver. Silver is renowned for its excellent conductivity, surpassing all other metals. To perform this test, you will need an ohmmeter:
  • Connect the ohmmeter to the sample to measure resistance.
  • Note that silver will show extremely low resistance values.
The lower the resistance, the higher the conductivity. A resistance close to that of silver indicates that the sample conducts electricity well, consistent with silver's properties. This characteristic is a significant indicator that your metal sample is likely silver.
Chemical Tests with Silver
Chemical testing reveals unique reactions that can further confirm the identity of silver. One such test involves using nitric acid (HNO鈧�) and potassium dichromate (K鈧侰r鈧侽鈧�). Here's how you can perform a chemical test:
  1. Dissolve a small piece of the metal in concentrated nitric acid to form a clear solution of silver nitrate if silver is present.
  2. Add potassium dichromate to the solution. If the metal is silver, a reaction should occur, producing a characteristic red solid known as silver chromate.
This red precipitate is a strong indicator of silver, allowing for a straightforward confirmation when visual assessments are not definitive.
X-ray Fluorescence Analysis
X-ray fluorescence (XRF) analysis offers a non-destructive way to determine the elemental composition of a metal sample. Here鈥檚 how it works:
  • The sample is exposed to X-rays.
  • The energy from the X-rays causes atoms in the sample to emit secondary X-rays, or fluorescence, at specific wavelengths.
  • For silver, these fluorescence peaks will appear at known characteristic wavelengths.
Using XRF can confirm the presence of silver by identifying these signature spectral peaks. It's a precise method to corroborate findings from previous tests such as density and conductivity measurements, providing a comprehensive analysis of the material's composition.

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Most popular questions from this chapter

A few years ago a young chemist in Vienna, Austria, wanted to see just how permanent the gold was in his wedding band. The ring was 18 -carat gold. (18-carat gold is \(75 \%\) gold with the remainder copper and silver.) One week after his wedding day he took off the ring, cleaned it carefully, and weighed it. It had a mass of 5.58387 g. He weighed it weekly from then on, and after 1 year it had lost \(6.15 \mathrm{mg}\) just from normal wear and tear. He found that the activities that took the greatest toll on the gold were vacationing on a sandy beach and gardening. (a) What are the symbols of the elements that make up 18-carat gold? (b) The density of gold is \(19.3 \mathrm{g} / \mathrm{cm}^{3} .\) Use one of the periodic tables on the Internet (such as www.ptable.com) to find out if gold is the most dense of all of the known elements. If it is not gold, then what element is the most dense [considering only the elements from hydrogen (H) through uranium (U)]? (c) If a wedding band is 18 -carat gold and has a mass of \(5.58 \mathrm{g}\), what mass of gold is contained within the ring? (d) Assume there are 56 million married couples in the United States, and each person has an 18-carat gold ring. What mass of gold is lost by all the wedding rings in the United States in 1 year (in units of grams) if each ring loses \(6.15 \mathrm{mg}\) of mass per year? Assuming gold is \(\$ 1620\) per troy ounce (where 1 troy ounce \(=\) 31.1 \(\mathrm{g}\) ), what is the lost gold worth?

Make a drawing, based on the kinetic-molecular theory and the ideas about atoms and molecules presented in this chapter, of the arrangement of particles in each of the cases listed here. For each case, draw 10 particles of each substance. It is acceptable for your diagram to be two dimensional. Represent each atom as a circle, and distinguish each different kind of atom by shading. (a) a homogeneous mixture of water vapor and helium gas (which consists of helium atoms) (b) a heterogeneous mixture consisting of liquid water and solid aluminum; show a region of the sample that includes both substances (c) a sample of brass (which is a homogeneous solid mixture of copper and zinc)

A copper-colored metal is found to conduct an electric current. Can you say with certainty that it is copper? Why or why not? Suggest additional information that could provide unequivocal confirmation that it is copper.

Identify the following as either physical changes or chemical changes. (a) The desalination of sea water (separation of pure water from dissolved salts). (b) The formation of \(\mathrm{SO}_{2}\) (an air pollutant) when coal containing sulfur is burned. (c) Silver tarnishes. (d) Iron is heated to red heat.

Carbon tetrachloride, \(\mathrm{CCl}_{4}\), a common liquid compound, has a density of \(1.58 \mathrm{g} / \mathrm{cm}^{3} .\) If you place a piece of a plastic soda bottle \(\left(d=1.37 \mathrm{g} / \mathrm{cm}^{3}\right)\) and a piece of aluminum \(\left(d=2.70 \mathrm{g} / \mathrm{cm}^{3}\right)\) in liquid \(\mathrm{CCl}_{4},\) will the plastic and aluminum float or sink?
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