I've been having trouble setting up word problems. Here is one problem I need help with.
How many Bromide ions are in a sample of CaBr2 that has a mass of 10.0g?
how many molecues of CaBr2 is in 10g?
molecules: 10/molmassCaBr2 * avag number
bromide ions, 2x the above number.
To solve this word problem, we need to use the concept of moles and Avogadro's number. Here's a step-by-step breakdown of how to tackle this problem:
Step 1: Determine the molar mass of CaBr2
The molar mass of CaBr2 is calculated by adding the atomic masses of calcium (Ca) and two bromine (Br) atoms:
Molar mass of CaBr2 = Atomic mass of Ca + 2 × Atomic mass of Br
The atomic mass of Ca can be found in the periodic table (40.08 g/mol), and the atomic mass of Br is also listed (79.90 g/mol).
Molar mass of CaBr2 = 40.08 g/mol + (2 × 79.90 g/mol) = 199.88 g/mol
Step 2: Determine the number of moles of CaBr2
To find the number of moles, we can use the relationship between mass, moles, and molar mass:
Number of moles = Mass / Molar mass
Given that the mass of the sample is 10.0 g, we can substitute these values into the formula:
Number of moles = 10.0 g / 199.88 g/mol = 0.050 mol
Step 3: Determine the number of bromide ions
In CaBr2, there are two bromide (Br) ions for every one CaBr2 molecule. This means that the number of bromide ions is twice the number of moles of CaBr2:
Number of bromide ions = 2 (moles of CaBr2)
Plugging in the value we found in step 2:
Number of bromide ions = 2 × 0.050 mol = 0.10 mol
Therefore, there are 0.10 moles or 0.10 × 6.022 × 10^23 bromide ions in a sample of CaBr2 that weighs 10.0 g.