Define matter. Which of the following are examples of matter? (a) air, (b) a pencil, (c) a cheese sandwich, (d) a squirrel,(e) your mother

Consider the balanced equation for the combustion of hexane, a component of gasoline:

$$2 \mathrm{C}_6 \mathrm{H}_{14}+19 \mathrm{O}_2 \longrightarrow 12 \mathrm{CO}_2+14 \mathrm{H}_2 \mathrm{O}$$

(a) How many atoms of $\mathrm{C}$ are on each side of the equation?
(b) How many atoms of $\mathrm{H}$ are on each side of the equation?
(c) How many atoms of $\mathrm{O}$ are on each side of the equation?

Consider the balanced equation

$$2 \mathrm{Fe}\left(\mathrm{NO}_3\right)_3+3 \mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{Fe}_2\left(\mathrm{CO}_3\right)_3+6 \mathrm{NaNO}_3$$

(a) How many atoms of $\mathrm{Na}$ are on each side of the equation?
(b) How many atoms of $\mathrm{C}$ are on each side of the equation?
(c) How many atoms of $\mathrm{O}$ are on each side of the equation?
(d) How many atoms of Fe are on each side of the equation?

How many atoms of each element are represented in each of the following expressions? (a) $7 \mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H}$, (b) $2\left(\mathrm{NH}_2\right)_2 \mathrm{CO}$, (c) $5 \mathrm{C}_3 \mathrm{H}_5(\mathrm{OH})_3$

How many atoms of each element are represented in each of the following expressions? (a) $\mathrm{3N_2O}$, (b) $\mathrm{4(CH_3)_2S}$, (c) $\mathrm{2CuSO_4.5H_2O}$

How many atoms of each kind are represented in the following formulas? For each, name the elements present. (a) $\mathrm{CH_3CH_2CO_2C_3H_7}$, (b) $\mathrm{MgSO_4.7H_2O}$, (c) $\mathrm{KAl(SO_4)_2.12H_2O}$, (d) $\mathrm{Cu(NO_3)_2}$, (e) $\mathrm{(CH_3)_3COH}$

A hand generator is connected to a coil of wire. A compass placed in the coil lines up with the axis of the coil when the generator handle is rotated. If the direction of the handle's rotation is reversed, what happens to the compass needle?

a) The needle rotates $90^{\circ}$.

b) The needle rotates $180^{\circ}$.

c) The needle spins continuously.

d) Nothing happens; the needle stays in place.

How many atoms of each kind are represented in the following formulas? For each, name the elements present. (a) $\mathrm{Ni(ClO_4)_2}$, (b) $\mathrm{COCl_2}$, (c) $\mathrm{K_2Cr_2O_7}$, (d) $\mathrm{CH_3CO_2H}$, (e) $\mathrm{(NH_4)_2HPO_4}$

How many atoms of each kind are represented in the following formulas? For each, name the elements present. $(a) \mathrm{H_3PO_4}$, $(b) \mathrm{Ca(H_2PO_4)_2}$, $(c) \mathrm{C_4H_9Br}$, $(d) \mathrm{Fe_3(AsO_4)_2}$, $(e) \mathrm{C_3H_5(OH)_3}$

How many atoms of each element are represented in each of the following formulas? For each, name the elements present. (a) $\mathrm{K}_2 \mathrm{C}_2 \mathrm{O}_4$, (b) $\mathrm{H}_2 \mathrm{SO}_3$, (c) $\mathrm{C}_{12} \mathrm{H}_{26}$, (d) $\mathrm{HC}_2 \mathrm{H}_3 \mathrm{O}_2$, (e) $\left(\mathrm{NH}_4\right)_2 \mathrm{HPO}_4$

How many atoms of each element appear on each side of the arrow in the following equation? (Hint: Recall that coefficients multiply the elements in the entire formula.)

$$4 \mathrm{NH}_3+3 \mathrm{O}_2 \longrightarrow 2 \mathrm{~N}_2+6 \mathrm{H}_2 \mathrm{O}$$

Can a theory be proved to be correct?

Rochelle salt is the tetrahydrate of $\mathrm{KNaC_4H_4O_6}$, which means there are four molecules of water per $\mathrm{KNaC_4H_4O_6}$. Write the formula for Rochelle salt.

Epsom salts is a hydrate of magnesium sulfate, $\mathrm{MgSO_4.7H_2O}$. What is the formula of the substance that remains when Epsom salts is completely dehydrated?