If it's to balance the equation then it's already balanced.
Answer:propanoic acid
Explanation:
Carboxylic acids contain the COOH group. This group is capable of hydrogen bonding leading to association of the molecules. Cyclobutane is a cyclic alkane and acetone is a ketone. Non of these compounds posses a polar -OH bond which is necessary for the occurrence of hydrogen bond. Hydrogen bonds only occur in carboxylic acids and alcohols. Hydrogen bond leads to molecular association and high boiling points.
15 because atomic no. is the number of protons
Mixture: matter than is composed of two or more substances that can be separated by physical means (ex; let's say you have a jar of red and blue marbles. this is a mixture. You can separate the colors with your hands (physical means.))
Compound: a substance in which two or more atoms are chemically combined in a fixed proportion (ex: water is a compound that consists of the element hydrogen and the element oxygen).