Question

1. calculate solve each of the following.

a. if 22.99 g of sodium and 35.45 g of chlorine fully react, how much sodium chloride forms?
b. a 12.2 - g sample of x reacts with a sample of y to form 78.9 g of xy. what mass of y reacted?

1. evaluate a friend tells you, “because composition does not change during a physical change, the appearance of a substance does not change.” is your friend correct? explain.

Explanation:

13a

Step1: Apply law of conservation of mass

In a chemical reaction, the total mass of reactants equals the total mass of products. Sodium (Na) and chlorine (Cl) react to form sodium - chloride (NaCl). The mass of reactants is the sum of the mass of sodium and chlorine.
$m_{reactants}=m_{Na}+m_{Cl}$
$m_{Na} = 22.99\ g$, $m_{Cl}=35.45\ g$
$m_{reactants}=22.99 + 35.45$

Step2: Calculate the mass of product

Since the mass of products is equal to the mass of reactants in a chemical reaction with no loss of mass, the mass of sodium - chloride formed is equal to the sum of the masses of sodium and chlorine.
$m_{NaCl}=22.99+35.45 = 58.44\ g$

Step1: Use law of conservation of mass

The chemical reaction is $X + Y
ightarrow XY$. According to the law of conservation of mass, $m_X + m_Y=m_{XY}$. We know $m_X = 12.2\ g$ and $m_{XY}=78.9\ g$.
We need to find $m_Y$, and we can re - arrange the formula $m_Y=m_{XY}-m_X$.

Step2: Calculate the mass of Y

Substitute the given values into the formula:
$m_Y=78.9 - 12.2=66.7\ g$

A physical change only affects the physical properties such as state (solid, liquid, gas), shape, or size of a substance, not its chemical composition. However, the appearance of a substance can change during a physical change. For example, melting ice (a physical change) changes ice from a solid to a liquid, and its appearance changes from a hard, white, solid to a clear, flowing liquid.

Answer:

$58.44\ g$

13b