Awhite powder is known to be a mixture of magnesium oxide and aluminum oxide. 100cm3 of 2moldm-3 naoh(aq) is just sufficient to cause the aluminum oxide in x grams of the mixture to dissolve. the reaction occurring is al2o3 + 2oh- + 3h2o > 2al(oh)4- 800cm3 of 2 moldm-3 hcl (aq) is just sufficient to cause all of the oxide in x grams of the mixture to dissolve. the reactions occurring are al2o3 + 6h > 2al3+ + 3h2o and mg2+ +h2o. how many moles of each oxide are present in x grams of the mixture ?
a. aluminium oxide 0.05, magnesium oxide 0.25
b. aluminium oxide 0.05, magnesium oxide 0.50
c. aluminium oxide 0.10, magnesium oxide 0.25
d. aluminium oxide 0.10, magnesium oxide 0.50

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.

the population of unionid mussels in the hudson river decreased after zebra mussels were introduced. zebra mussels, a nonnative species, competed with the unionid mussels for food. the zebra mussels were able to outcompete the unionid mussels, allowing the zebra mussel population to increase dramatically over six years. the unionid mussel population decreased due to a lack of food.

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