a. How many hydrogens does an alkane with 17 carbons have?
b. How many carbons does an alkane with 74 hydrogens have?

Verified step by step guidance

1. Step 1: Recall the general molecular formula for alkanes, which is C_nH_2n+2. This formula applies to saturated hydrocarbons (alkanes) with no rings or double bonds.
2. Step 2: For part (a), substitute n = 17 (the number of carbons) into the formula H_2n+2. This gives H = 2(17) + 2. Simplify the expression to determine the number of hydrogens.
3. Step 3: For part (b), use the same formula, H_2n+2, and set H = 74 (the number of hydrogens). Solve the equation 74 = 2n + 2 for n (the number of carbons). Subtract 2 from both sides and then divide by 2 to isolate n.
4. Step 4: Verify your results for both parts by substituting the calculated values back into the formula C_nH_2n+2 to ensure they satisfy the relationship.
5. Step 5: Conclude by stating the number of hydrogens for part (a) and the number of carbons for part (b), ensuring the answers align with the alkane formula.

Key Concepts

Alkane General Formula

Alkanes are saturated hydrocarbons with the general formula CnH2n+2, where 'n' represents the number of carbon atoms. This formula indicates that for every carbon atom in an alkane, there are two hydrogen atoms plus two additional hydrogens. Understanding this formula is essential for calculating the number of hydrogens based on the number of carbons in an alkane.

Hydrocarbon Structure

Hydrocarbons are organic compounds consisting solely of carbon and hydrogen atoms. Alkanes, as a specific type of hydrocarbon, have a tree-like structure with single bonds between carbon atoms, leading to a saturated configuration. This structural characteristic influences their chemical properties and reactivity, which is important when determining molecular formulas.

Molecular Formula Calculation

Calculating the molecular formula of alkanes involves applying the general formula to derive the number of hydrogen atoms from the number of carbon atoms, or vice versa. For example, if given the number of hydrogens, one can rearrange the formula to find the number of carbons. This skill is crucial for solving problems related to the composition of alkanes.