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ALEKS CHEM Prep Questions and Answers 100% Correct
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Exam of 3 pages for the course ALEKS at ALEKS (ALEKS CHEM Prep)
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ALEKS CHEM PrepSteps for counting sigfigs - answer1. Find first nonzero digit, start from left to right
2. Count digits from this digit to the right including any zeros
When converting units it is simpler to have - answerThe power of ten 10^x in front of the
basic unit ex 1nm=10^-9m
If there are numbers written after chemical symbols it tells you - answerThe atomic
mass # ex: Pm-149, 61 protons and 149-61 neutrons
Steps to converting mass to mols - answer1. Find the molar mass (which is atomic
mass g•mol^-1) ex: molar mass of calcium is 40.078 g•mol^-1
2. Take the weight (g) that's weighed out and divide by the molar mass to get how many
moles were weighed out
3. Your answer will be in the form of # 1/mol^-1 —> bring mol to numerator: #mol
Density is defined as - answerp=m/v (g•cm^3)
How do you count the number of valence electron of main group elements - answer3 of
valence electrons= group #
Whats the exception for counting the number of valence electrons in main group -
answerHelium has 2 valence and not 8
How to convert Celsius to Kelvin - answerT(C)=T(K)-273.15
Rules for writing down chemical formulas based on structure or model - answer1.
Capitalize the First letter of symbol for element
2. Use subscripts to show # of atoms of each element
3. Write (H) before all elements
4.Write (H) after elements in groups 6a and 7a
5. If it's a molecule with just hydrogen and one other element from group 6a or 7a then
write (H) first
How to count sigfigs when + or - - answerIts only signif if all measurements go that far
ex; 15.50 + .7 = to a number that goes as far as only the first decimal place
When counting valence electrons of an atomic ion - answerThe charge determines if it
loses or gains electrons Ex; Te^- has an extra electron
Atomic number tells - answernumber of protons and electrons
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